Extreme heat events are periods of abnormally hot weather generally lasting more than two consecutive days.
More deaths occur related to heat in New York City and the United States annually, on average, than as the result of any other extreme weather event. New York City is particularly susceptible to this hazard due to its dense urban environment and materials used to support the built environment, which absorb and trap heat. Prolonged periods of increased temperatures and humidity create a dangerous situation for individuals at greater risk for heat-related illness and strain the city’s utilities and infrastructure. Climate scientists project that, in association with climate change, average temperatures will rise and heat waves will become more frequent, intense, and prolonged.
What is the Hazard?
During the summer, New York City usually experiences one or more periods of extreme heat. Heat is not only uncomfortable, it can also be dangerous – causing dehydration, heat exhaustion, heat stroke, worsening of several chronic and mental health conditions, and in severe cases, death. Periods of extreme heat can also lead to pressure on the power grid, causing outages that can create cascading negative impacts throughout the city.
Extreme heat events are most likely to occur between June and August, but they sometimes occur as early as May and as late as September. Higher temperatures and humidity in these fringe months can also become dangerous when combined with extreme physical exertion, increasing the risk of heat exhaustion. Each summer, on average, an estimated 350 New Yorkers die prematurely because of hot weather in NYC. These heat-related deaths account for about 2% of all deaths over the warm season months of May through September.
Between 1981 and 2020, temperatures in Central Park reached 90°F or higher for about 18 days per year. In New York City, extreme heat events are defined as periods when the heat index is 100°F or higher for one or more days, or when the heat index is 95°F or higher for two or more consecutive days, based on analyses of heat and mortality risk in the city. . It’s important to note that the definition of ‘extreme heat’ can vary by location, based on local climates and regional factors. Nevertheless, regardless of the specific definition, the risk of people and infrastructure suffering adverse effects from extreme heat generally increases with the intensity and duration of a heatwave. Collectively, the frequency of multiple heat waves could also produce damages to people, property and infrastructure over time.
Hazards from extreme heat are made worse when accompanied by high levels of humidity – the amount of moisture in the air. As the temperature climbs, the air can hold more moisture. High humidity hinders a person’s body from cooling down naturally, leading people to perceive that the temperature feels hotter. The combination of temperature and humidity – what the temperature “feels like” – is known as the heat index.
Recent events have underscored the potential risks associated with unseasonably warm weather. For instance, in 2022, challenges were faced during prominent outdoor events such as the RBC Brooklyn Half Marathon and the NYC Marathon, where participants faced difficulties due to high temperatures and humidity. It is essential to consider these incidents in relevant contexts, such as outdoor athletics and exertion, to understand the broader implications of changing climate patterns.
Extremely poor air quality is another hazard that often accompanies extreme heat. During New York City’s summer months, stagnant atmospheric conditions trap humid air and pollutants, such as ozone, near the ground.
Climate change is likely to bring hotter temperatures and more hot days, leading to far longer and more frequent heat waves.
The National Weather Service (NWS) uses a heat index chart to determine the effects particular combinations of temperature and humidity will have on the general population.
Note that the heat index values used in this chart are calculated in the shade and are not adjusted for different levels of sun exposure. Thus, when people are exposed to direct sunshine, they can feel much hotter than the temperature indicated on this chart. During hot weather, the stress a person experiences from the heat depends upon: the temperature, location, and air movement as well as level of physical activity, individual age and health status, and exposure to sunlight and radiant heat from nearby surfaces. If indoors, where people spend the majority of their time, the presence or absence of air conditioning is a critical factor in how much heat someone experiences.
To warn the public when extreme heat is forecast, the NWS provides New York City with heat-related “products” in the form of Heat Advisories, Excessive Heat Watches, and Excessive Heat Warnings. The Heat Advisory level is based on analysis of historical weather and mortality data by the New York City Department of Health and Mental Hygiene (DOHMH).
To help respond to extreme heat events, the NWS worked with DOHMH and New York City Emergency Management (NYCEM) to determine specific criteria for issuing heat products in New York City.
NWS Extreme Heat Products for the New York City Region
|Heat Advisory (NYC)
|Issued within 24 hours prior to the onset of any of the following conditions:
– Heat index of 100°F – 104°F for any period
– Heat index of 95°F – 99°F or greater for two consecutive days
|Excessive Heat Watch
|Issued 24 – 48 hours prior to the onset of the following condition:
– Heat index of at least 105°F for at least two consecutive hours
|Excessive Heat Warning
|Issued within 24 hours of the onset of the following condition:
– Heat index of at least 105°F for at least two consecutive hours
When the NWS issues an extreme “heat product,” it:
- Includes heat index values and city forecasts.
- Identifies potential impacts and recommends precautionary and preparedness actions. These actions may include clarifications as to who is at greatest risk, safety rules for reducing risk, and the extent of hazard and heat index values.
- Assists state and local health officials to prepare civil emergency messages.
Official temperature readings for New York City are taken near Belvedere Castle in Central Park, although temperatures vary throughout the city. The 2019 New York City Panel on Climate Change (NPCC) report estimated that from 1971 to 2000, New York City had an average of 18 days per year with maximum temperatures at or above 90°F and had heat waves lasting an average of four days. This NPCC calculation uses a time period (1971 – 2000) that differs from the time period used by meteorologists (1981 – 2010).
According to the 2023 NPCC report, from a baseline of 17 days at or above 90 degrees (using the 1981-2010 period), projections indicate up to 54 days at or above 90 by the 2030s; 69 days by the 2050s; and 108 days by the 2080s. The duration of heatwaves is also anticipated to increase, moving from a baseline average of 4 days to 6 by the 2030s, remaining at 6 by the 2050s, and reaching 10 by the 2080s.
Drawing from historical NWS data recorded at Central Park, there’s been a discernible rise in the annual number of days with high temperatures of 90°F and above since the late 19th century. The 2023 interim report adds that this trend equates to an increase of 0.47 additional days above 90 per decade at Central Park, 1.07 additional days per decade at LaGuardia, and 1.35 additional days per decade at Newark.
In the future, the number, duration, and intensity of heat waves at or above 90°F are expected to continue to increase as a result of climate change. These trends are discussed further in the Future Environment.
The built environment of New York City results in the phenomenon known as the “urban heat-island effect.” Heat islands develop in urban areas where formerly vegetated, permeable surfaces are now paved with asphalt or covered by buildings and other structures that absorb and retain heat. This condition impedes the overnight cooling process, keeping nighttime air temperatures significantly higher than temperatures in surrounding rural areas. Waste heat that emanates from city air conditioners, vehicles, and other types of equipment also contribute to the urban heat island effect.
The built environment and land use patterns also cause some neighborhoods to be warmer than others. Not surprisingly, areas with the highest building density, most vehicle traffic, (highest concentrations of heat-trapping built structures) and the least vegetation have higher temperatures. The below thermal image of New York City reflects the temperature variation in different neighborhoods. Warmer locations are shown in orange and red, while cooler areas are shown in green and yellow.
The second map displays the city’s vegetative cover. New York City hotspots are generally areas that lack any type of vegetation. New Yorkers living in these areas of the city are most exposed to high heat events, particularly among residents who do not have access to air conditioning.
Since the late 19th century, the number of days that New York City has experienced with temperatures of 90°F or higher has increased. The NPCC report notes that climate scientists predict that by the 2050s, New York City could experience as many 90°F days annually as Birmingham, Alabama, does today – more than triple the 18 days we experience in an average year.
For more information on historic heat events, use the Hazard History and Consequence Tool, an interactive tool developed for this website.
What is the Risk?
More heat-related deaths occur in New York City and the United States annually, on average, than casualties resulting from any other type of extreme weather event as shown in the below chart.
Periods of extreme heat put pressure on New York City’s infrastructure. Heat waves cause people to increase their usage of air conditioning, which can strain the power grid and trigger power outages; power outages in turn, can lead to adverse health impacts. Transportation infrastructure is vulnerable in terms of buckling and melting of road services and warping of train fails and wheels (FTA).
Scientists predict that in the future, extreme heat events in New York City will increase in frequency, intensity, and duration.
One of the main impacts of heat is to human health. If a person has prolonged exposure to very high temperatures they can experience serious health problems, including dehydration, heat exhaustion, heat stroke and, in severe cases, death. Symptoms of heat exhaustion include confusion, dizziness, fatigue, nausea, headaches, and muscle cramps. Without proper treatment, heat exhaustion may progress to heat stroke. Moreover, the color of roofs and walls in urban settings can significantly influence local temperatures, with darker colors absorbing more heat and potentially exacerbating the effects of extreme temperatures on individuals.
Heat stroke, the most serious of heat-related illnesses, occurs when the body is no longer able to maintain a core body temperature in the normal range. Common symptoms include hot, dry skin; seizures; disorientation; and loss of consciousness. Heat stroke can cause complications in the central nervous system and permanent damage to the brain and other vital organs. In many cases, heat stroke can result in death.
Prolonged periods of heat can also exacerbate certain chronic conditions, including renal, cardiovascular, and respiratory illnesses, which sometimes also result in death. These deaths, also known as “excess deaths” or “heat-exacerbated deaths” are much greater in number than heat stroke deaths (see “Excess Deaths” box below for information on how these deaths are estimated).
Each summer, an estimated 350 New Yorkers die prematurely because of extreme heat, according to the 2023 NYC Heat-Related Mortality Report. This includes an average of 345 heat-exacerbated mortality and 7 heat stroke deaths. About 115 of these heat-exacerbated deaths are attributed to extreme heat days, and the rest are attributable to hot, but not extreme, days, which have been increasing in number more quickly than extreme heat days. The average number of these hot but non-extreme heat days increased from 52 in 1971-1975 to 74 days in 2016-2020, whereas the number of extreme heat days only increased from 4 in 1971-1975 to 11 in 2016-2020.
In addition, there are about 600 emergency department visits and hospital admissions for direct heat-related illness, and increases in ED and hospital visits for kidney (renal) conditions, heart and respiratory conditions, and mental health conditions, among others.
In New York City, most heat-related deaths and illness could be prevented using home air conditioning. Approximately 80 percent of heat stroke deaths among New Yorkers are due to prolonged heat exposure at home. Heat-exacerbated deaths are also more likely to occur at home during extreme heat. The high expense of purchasing and running a home air conditioner is an economic barrier that places many lower-income New Yorkers at risk. According to a random digit dial telephone survey conducted from September 22 to October 1, 2015, 13 percent of NYC adults aged 18 and older did not possess an air conditioner (AC), and another 15 percent used AC never or infrequently. This highlights that without air conditioning, indoor temperatures can be significantly hotter than outdoors during and shortly after periods of extreme heat.
About 91% of NYC households have home air conditioning. There are inequities in access to air conditioning by neighborhood, however, with coverage up to 98% in some higher income neighborhoods and as low as 76% in lower income neighborhoods.
For more information on heat-related illness, visit the DOHMH Environment and Health Data Portal.
Vulnerable Neighborhood Communities
The neighborhood where a person lives may also be a factor in residents’ risk for heat-related illness or death during hot weather. People living in certain areas and communities in New York City may be at higher risk than others during periods of extreme heat.
The Heat Vulnerability Index (HVI) is based on an analysis of heat-related mortality in New York City and provides a measure of how at risk a neighborhood is during extreme heat events compared to other neighborhoods.
As shown, the New York City communities with highest vulnerability to death or illness during periods of extreme heat have the following characteristics of higher surface temperatures, less green space, and lower median income, and non-Hispanic black populations. This is a result of historical disinvestment, racism, and segregation.
The HVI enables New York City to prioritize resources to communities identified as having a high risk to the adverse health impacts of extreme heat. Actions taken by New York City include programming to promote social cohesion, outreach efforts to educate residents about heat risks, coating roofs white and installing green roofs were feasible, and planting street trees through Cool Neighborhoods NYC. These actions are part of a comprehensive initiative to keep New York City communities safe in extreme heat.
However, it is important to note that residents are still at risk for heat illness and death even if they reside in neighborhoods with low HVI scores. While some neighborhoods are more vulnerable to heat than others, there are vulnerable populations and individuals in every single neighborhood in NYC.
Individuals at Increased Risk during Power Outages
When energy demand is high during heat waves, power outages can occur – a situation that can put certain members of the community at risk. Power outages create risk for anyone who relies on life-sustaining medical equipment, oxygen concentrators, rechargeable motorized wheel chairs, and refrigerated medications, as well as certain at-risk groups who require air conditioning to stay safe during heat waves.
If pharmacies cannot operate due to a power outage, anyone relying upon them to refill necessary prescriptions is placed at risk.
If building elevators become inoperable during power outages, people with disabilities or access and functional needs are at greater risk because they may be unable to obtain the goods and services that they need.
Architecture and infrastructure can each contribute to New York City’s extreme heat risk.
Architecture and Heat
People who live and work in New York City can be placed at higher risk of heat related illness if their building’s architecture traps heat, limits ventilation, or if the cooling systems do not work or are absent entirely.
A building’s construction materials can affect its internal temperature, potentially increasing the heat for workers or residents. Factors that can affect a building’s internal temperature include – the amount of air that escapes through gaps or cracks in the walls, the amount of insulation in the walls and roofs, the type and size of windows, and the materials with which a building is constructed, as well as the direction the building faces and, for apartments, the floor on which it is located.
While glass transmits heat more readily than materials like brick, masonry, and wood, leading to an internal greenhouse effect on hot days, it’s important to note that buildings with glass facades are often newer and may have effective air conditioning systems. These buildings might not typically house vulnerable populations. However, it’s crucial to acknowledge that not all residents in such buildings might have equal access to cooling resources.
Conversely, older buildings may lack sufficient insulation or ventilation as per current codes, allowing more hot air to enter. They might also have electrical systems that are not equipped to handle the load of modern air conditioners. During extreme heat events, these factors can contribute to a rapid increase in indoor temperatures.
In addition to trapping hot air inside buildings, certain building materials can increase local temperatures outside. For example, asphalt roofs, adjacent parking lots, or mechanical systems that pump out heat or hot vapor into sidewalks, can all produce and trap heat that is felt outdoors at street level. To mitigate this, strategies such as using materials with higher solar reflectance and thermal emittance for roofs, as suggested by the NYS Energy Code 2020, are essential. Improving the design of areas exposed to the environment, like rooftops, building facades, and landscaping, and reducing internal cooling usage can help decrease the amount of heat expelled to the surrounding area, ultimately contributing to a cooler outdoor environment.
The Grid and Risk of Power Outages
A period of extreme heat in New York City increases the population’s reliance upon air conditioning — a necessary health safeguard for people in certain at-risk groups during hot weather. However, reliance upon air conditioning during a heat wave increases the demand for electricity. If demand outstrips the power grid’s capacity to supply electricity, the population is at risk from power blackouts. New York City’s utility providers understand that they must take precautions to reduce strain on the system and avoid blackouts. To help manage these risks, New York City advises the public to set air conditioning at 78°F or low cool. This enables residents to maintain a healthy and comfortable indoor environment, lower their electricity bills, and minimize strain on the electric grid. Not only does excessive heat reduce energy efficiency, but it can physically damage electric generation, transmission, and distribution infrastructure; as more electricity flows through these systems to meet higher demand, the systems are increasingly stressed. Power lines can overheat and short circuit, potentially causing power outages. Heat can also cause overhead electric and telecommunications lines to sag onto trees, creating a risk of short circuiting that may cause an outage.
Power outages can have severe, pervasive impacts both on people and the built environment. In the absence of backup power, power outages can shut down all types of equipment that are plugged into the grid including air conditioners, elevators, electric pumps that distribute water to the upper floors of high-rise buildings, refrigerators, freezers, and computers. People who depend upon life-sustaining medical equipment, oxygen concentrators, rechargeable motorized wheelchairs, and refrigerated medications are especially at risk.
A citywide power outage that occurred in August 2003 on a normal summer day – not during a heat wave – produced approximately 90 excess deaths. Hospital admissions also increased for respiratory conditions and medical device failures., A widespread outage during a heat wave could cause even more deaths and hospital visits. Already, 311 complaints about power outages are more likely to be placed from neighborhoods with more residents who are low-income and have higher heat vulnerability.
Extreme heat poses a risk to the extensive network of ground transportation infrastructure serving New York City. High temperatures can cause damage such as cracking, buckling, or sagging of railroad tracks, wires, and pavement on roads and bridges. These effects can lead to service disruptions, hazardous travel conditions, and costly repairs. The impact of heat on infrastructure, while not often singled out in cost estimates, can be considerable. For example, heat-related costs to railways have been noted to be substantial, potentially increasing in the future.
Another concern during extreme heat events is the illegal opening of fire hydrants for use as sprinklers to cool off. This can result in a drop in water pressure throughout the system, which might reduce firefighting capabilities and increase risk for first responders and citizens in emergencies. To mitigate this issue, the New York City Fire Department (FDNY) distributes hydrant spray caps to the public. These caps reduce the discharge of open hydrants from approximately 1,000 gallons per minute to 25 gallons per minute, helping to maintain water pressure.
Public concern regarding service disruptions from heat is reflected in opinion surveys, indicating an increasing perception of global climate change and warming as significant threats. These disruptions, combined with the increasing awareness of climate issues, underscore the need for continued attention to the resilience of infrastructure against extreme heat.
Ecosystems and Natural Areas
It is difficult to determine whether the extreme temperatures alone present any direct risk to the natural environment in New York City, since heat waves are naturally occurring weather events. Human activities and New York City’s dense built environment exacerbate the amount of heat here, but do not directly cause the problem.
Secondary hazards associated with extreme heat are poor air quality and drought, which put New York City’s natural environment at risk. Periods of hot weather trigger increases in energy use, which in turn contribute to higher emissions of pollutants and greenhouse gases.
Long-term temperature changes from an increasingly warmer climate may cause shifts in habitat and cause some local species to go extinct if they are not adapted to withstand long stretches of extreme heat or cold. In terms of short-duration extreme temperature events, it is still uncertain what impacts this may have on the natural environment, if any.
Poor air quality can occur during heat waves when stagnant atmospheric conditions trap pollutants in urban areas. Ozone, a major component of smog, is created when pollutants emitted by cars, power plants, industrial boilers, and other sources chemically react in the presence of sunlight. Hot weather can increase ozone levels, causing or worsening people’s respiratory problems.
The U.S. Environmental Protection Agency Air Quality Index (AQI) was created to correlate levels of different pollutants to a single scale. The higher New York City’s AQI value on the scale, the greater the health concern. The New York State Department of Environmental Conservation’s Bureau of Air Quality Surveillance is responsible for the operation of the various ambient air quality monitoring networks for the State.
When levels of ozone and/or fine particles are anticipated to exceed an AQI value of 100, New York State Department of Environmental Conservation and the State Department of Health issue an Air Quality Health Advisory to alert people with high sensitivity to take necessary precautions. When ozone levels are projected to reach the unhealthy range, people are advised to limit vigorous outdoor physical activity during the afternoon and early evening hours.
Scientists predict that in the future, extreme heat events in New York City will increase in frequency, intensity, and duration. This table, adapted from the 2023 New York City Panel on Climate Change (NPCC), illustrates this projected change through the middle of the 21st century. These projections are relative to the period of 1981-2010 and include a middle-range estimate (25th-75th percentile) and a high-end estimate (90th percentile).
|Middle Range (25th – 75th percentile)
|High End (90th percentile)
|Middle Range (26th – 75th percentile)
|High End (90th percentile)
|Number of days per year at or above 90 °F
|Number of heat waves per year
|Average duration (days)
|5 – 6
According to NPCC projections, New York City can expect, on average, up to 215 to 52 additional days where temperatures reach 90°F or above by the 2050s, and up to 29 to 91 additional days at 90°F or above by the 2080s. This projection for the 2080s represents at least double what New York City experiences today.
Compared to the number of heat waves that New York City experiences annually, these projections estimate that this area will have up to 4 to 8 heat waves per year by the 2050s, and as many as 10 heat waves per year by the 2080s. On average, the NPCC estimates that New York City’s heat waves will last one to six days longer. As the climate changes and warms, extreme heat events are expected to become more common during May and September, the peripheral summer months.
The combination of an increased number of heat waves, higher average temperatures, and the projected changes in New York City’s demographics (such as an increase in its over 65 age population) are likely to lead to higher rates of temperature-related mortality and illness during high-heat events in the future unless there is adequate adaptation.
How to Manage the Risk
Extreme heat events, which are projected to increase in frequency and severity in New York City over the next few decades, can have significant consequences for at-risk populations and infrastructure – a situation that calls for implementation of more comprehensive risk management strategies.
Some of the most important near-term strategies include informing at-risk populations about health risks, taking measures to insulate infrastructure from increased stress during heat waves, keeping internal building temperatures cool, and mitigating the urban heat island effect through more trees, vegetation, and reflective surfaces.
Public Education, Communication, Outreach, and Assistance
Before a heat wave strikes, the public – especially at-risk populations – must be understand the dangers of prolonged exposure to extreme heat, the types of people that are most at risk and why, and the practical measures people can take to protect themselves, their families, and their neighbors.
Experiences of severe heat waves in other cities have led New York City to enhance its own risk management strategies.
New York City has implemented several initiatives to mitigate the risks to residents, especially vulnerable populations, before heat waves occur. These initiatives are aimed at promoting resiliency to current extreme conditions and adapting to future increases in temperature:
- Prevention: As part of the Cool Neighborhoods NYC strategy, coordinated by the New York City Mayor’s Office of Climate and Environmental Justice (MOCEJ), DOHMH works with different partners to promote heat resiliency. This included DOHMH’s Be A Buddy program, a community-led pilot project to develop and implement strategies to promote social cohesion and increase community resilience for extreme heat, power outages, and other extreme weather.
- Outreach: The City conducts outreach to the general public and their partners — healthcare providers, community groups, faith groups, and service-agencies — by providing advice on how to mitigate risk from extreme heat. Outreach includes press releases, social media posts, in-person training and workshops for health care workers, community groups, and the public, and direct electronic communications to partners. During heat emergencies, the City encourages its partners and the public to check on clients, neighbors, family, and friends who may be at increased risk for heat-related illness during periods of hot weather.
- Publications: The Ready New York website “Beat the Heat,” published by NYCEM supplies important safety tips and other information online and in print. DOHMH also supplies information to the public and to health care providers about the health impacts of heat and heat illness prevention.
- Financial assistance: Cooling assistance is available to New York City residents through the Home Energy Assistance Program (HEAP), a federally funded program administered by the New York State Office of Temporary and Disability Assistance and the New York City Department of Social Services (DSS). People may qualify for financial aid to purchase and install an air conditioner, if they meet HEAP’s income criteria and have documentation of a medical condition that is exacerbated by heat.
- PlaNYC addresses extreme heat in a few ways. The plan aims to develop a maximum summer indoor temperature policy to protect all New Yorkers from extreme heat by 2030, including mandatory cooling requirements for new construction by 2025 and to reform of the Home Energy Assistance Program to cover both equipment and energy costs for cooling for low-income New Yorkers. It also set a goal of achieving at 30% tree canopy cover and installing 1 million square feet of cool roofs annually.
In response to the combined threats of the COVID-19 pandemic and extreme heat, on May 15, 2020, New York City announced the creation of the Get Cool NYC emergency program. Managed by NYC Emergency Management (NYCEM), this initiative distributed and installed nearly 73,000 free home air conditioners to low-income adults aged 60 and older who did not have a working home AC, targeting both residents in New York City Housing Authority (NYCHA) public housing and private housing. One study found that those who participated in the program were less likely to report feeling sick from the heat compared to those who did not participate. They were also more likely to report staying home on hot days.
During heat waves, New York City and its partners take the following actions to keep vulnerable populations and the general public safe:
- Advisories: NYCEM closely monitors NWS heat advisories, excessive heat watches and warnings. When conditions warrant, NYCEM activates New York City’s Heat Emergency Plan, which was developed jointly with the NWS, DOHMH, and other partners.
- Alerts: During heat emergencies, alerts and safety tips are disseminated to the public through Notify NYC and to organizations serving vulnerable populations through the Advance Warning System. Health care providers receive alerts through the Health Alert Network and other DOHMH channels.
- Cooling Centers: During heat emergencies, cooling centers are opened at designated locations, such as community centers, senior centers, and public libraries, to provide access to air-conditioned spaces to anyone who needs to escape the heat. Studies show that spending as few as two hours a day in an air-conditioned space can significantly reduce a person’s risk from heat-related illnesses. During the summer of 2022, New York City had over 500 air-conditioned spaces available, including 16 pet-friendly facilities.
- Outreach to homeless populations: During extreme heat events, outreach teams redouble round-the-clock outreach and engagement efforts citywide. Street homeless outreach teams are trained on heat stroke and other health and safety issues and reminded of criteria to enact removals under State law during weather emergencies (individuals must be at risk themselves or posing a risk to themselves or others). No one who is homeless and seeking shelter in New York City during an extreme heat event will be denied. Should any New Yorker see an individual who appears to be homeless and in need out in the heat, please call 311 and an outreach team will be dispatched to offer assistance.
- Support during outages: During outages, utility providers such as Con Edison and PSEG will conduct outreach to customers who have registered as being dependent on Life Support Equipment.
Government agencies and private sector entities pursue a wide range of short- and long-term strategies to manage risks associated with heat-related hazards to infrastructure. Some long-term initiatives have the critical short-term benefit of reducing demand on the power grid and the associated risk of power outages.
Utilities employ “supply-side” strategies to reinforce strain on the system and continue operations during extreme heat events:
- System reinforcements provide alternate or additional infrastructure capacity to minimize the risk of disruption due to heat – for example, by increasing the number of power supply feeders, upgrading to higher capacity cables, installing or upgrading more distribution transformers, building new substations, and redistributing electric loads among substations.
- Improving system reliability safeguards system components so that they are operational and available for service. This includes inspecting and maintaining equipment, repairing components, and implementing improvements such as redesigning circuits to minimize the number of customers affected, rebalancing demand across supply feeders, installing automated switches and monitoring equipment, as well as performing mobile scanning of city streets to reduce the risk of contact voltage.
- Operational readiness involves measures to prepare system operations for summer conditions and respond to events as they occur. This includes conducting engineering analyses and studies to assess system conditions, implementing protective steps such as voltage reduction, instituting the Incident Command Structure (ICS) for forecasted peak heat days, activating special resource teams such as cooling and event triage teams, conducting staff training and exercises on how to handle extreme heat scenarios, and confirming that power generators have adequate capacity.
- Pre-position back-up generators if a system is potentially vulnerable due to projected demand.
The city’s primary utility providers, Con Edison and PSEG, are strengthening their power sources and energy infrastructure by making utility systems more flexible and by diversifying energy sources to minimize impacts of extreme weather events. Utilities also employ “demand-side” strategies to manage load on the system and continue operations during extreme heat events:
- Utility demand response and energy efficiency programs are short and long term strategies that offer financial incentives to customers to help reduce overall energy consumption and peak demand on hot days. Con Edison runs aggressive demand-response programs in which commercial, industrial, and residential customers can enroll voluntarily. When demand for electricity soars, Con Edison pays those customers who temporarily reduce their consumption of electricity upon request. Con Edison’s energy efficiency programs offer customers rebates when customer install new energy efficiency and control equipment.
- Installing Advanced Metering Infrastructure (AMI). AMI, or “smart meters,” will assist customers in controlling energy use and demand as well as allow Con Edison to know immediately where customers are experiencing power outages and better coordinate restoration.
- Following a 2019 climate change vulnerability study, Con Edison created a Climate Change Implementation Plan, which outlines how they will make their systems more resilient to the effects of climate change. Con Edison’s 2023 Climate Change Vulnerability Study states that temperatures are rising quicker than previously projected and notes that heat-related resilience projects may need to be accelerated and implemented a decade earlier than planned. High temperatures were deemed to be a primary vulnerability for underground distribution and overhead transmission, and a secondary vulnerability for overhead distribution and key Con Edison facilities.
Transportation systems can be protected from hazards associated with periods of extreme heat with measures such as:
- Equipment upgrades to rail systems, which involves replacing or retrofitting system components, such as tracks, wires, signals, and switches.
- Retrofitting roads and bridges with heat-resistant materials to prevent cracking and buckling from thermal expansion.
The Metropolitan Transportation Authority (MTA) has invested in ways to protect its systems and equipment from heat-related damage, such as implementing new redundancy measures and making structural improvements to trains, railroad tracks, and buses.
New York City’s Department of Transportation (DOT) is studying the use of permeable pavements for its roads and bridges. The greatest advantage of deploying these types of pavements is to reduce the impacts of heavy precipitation and snowmelt; however, use of these materials, which remain cooler than typical roadway surfaces during summer months, may also reduce the damage to road surfaces during from heat waves.
Several long-term strategies in New York City aim to increase the energy efficiency of buildings, and lower indoor air temperatures – steps that help to reduce energy consumption over the long-term. These strategies with New York City’s built environment can reduce the risk of power outages and reduce reliance on other short-term strategies, such as utility demand-response programs.
The City has enacted new laws and regulations to promote energy-efficiency in new and existing building construction. Local Law 97, enacted in 2019, is a part of New York City’s Climate Mobilization Act that aims to reduce greenhouse gas emissions from buildings. The law sets carbon caps for buildings over 25,000 square feet, covering nearly 50,000 properties across NYC. Starting in 2024, the law will phase in carbon caps over time, becoming more stringent over a series of compliance periods through 2049. By 2050, all buildings will have to meet zero emissions requirements. The law assigns emissions limits for 60 different property types, reflecting the wide variation in energy use among buildings. These limits will decrease over five compliance periods, meaning each building will be allowed to emit less carbon over time.
Complementing this, Local Laws 92 and 94, also enacted in 2019, require the installation of sustainable roofing systems on all new buildings and major renovations where the entire roof deck or assembly is replaced. These laws stipulate the use of green or solar roofs, or highly reflective materials when these options are not feasible, contributing to the city’s goal of carbon neutrality by 2050.
Additionally, changes to the Construction Code have promoted sustainable building design by allowing the construction of green roofs previous code required building owners to obtain special permission for this type of construction. The Construction Code also requires that building owners use heat-reflective coverings on any roof having a less-than-25-percent slope. The 2012 Zone Green Text Amendment changed New York City’s zoning provisions to exclude green roofs from height limitations.
Many buildings have been designed and constructed to achieve performance standards that exceed the minimum required in New York City’s Construction Codes, and to keep internal building temperatures low through energy efficiency. These high-performance buildings use advanced designs and construction techniques — windows that keep cool air from escaping during summer, rigorous air sealing, and extensive insulation.
The New York City Mayor’s Office released PlaNYC in 2023 which outlines initiatives to make NYC safer, more vibrant, and more resilient to climate change impacts.
Existing buildings in New York City can benefit from retrofits so that their energy consumption is lower during periods of extreme heat. Several types of energy-efficient improvements can be made:
- Proper sealing and insulation keep buildings cooler by stopping cooled air from leaking out. Owners of existing buildings can caulk and seal doors and windows that leak air, and caulk and seal air leaks in walls, floors, or ceilings where openings exist for plumbing, ducts, or electrical wiring. The proper insulation of walls and attics also help, because insulation slows the transfer of heat into a building’s interior.
- High-performance materials, such as multiple-paned windows with reflective coatings, can be used to insulate buildings from extreme heat and keep cool air from escaping. Energy-efficiency retrofits, such as higher-efficiency mechanical systems and smart sensors, can reduce energy demand, decreasing the strain on the electric grid.
- Application of “cool roofs” – white, reflective surfaces to rooftops, which reduces cooling costs, cuts energy usage, lowers greenhouse gas emissions, and extends the lifespan of the roof. The coating used on the rooftops is highly reflective and quickly releases heat, which results in reduced absorption of solar heat leading to cooler buildings. Temperatures within the top floors of a building can be reduced by up to 30 percent. Aside from the benefits for the coated buildings, clusters of white rooftops reduce temperature in the surrounding areas and combat the urban heat island effect. City law requires the application of reflective coatings on new roofs and those that are undergoing significant repairs or replacement.
NYC CoolRoofs, a partnership between the New York City Department of Small Business Services (SBS), its Workforce1 Industrial & Transportation Career Center, MOCEJ, and The HOPE Program, promotes and facilitate the cooling of New York City’s rooftops by installing a reflective coating to dark roofs. The program provides free cool roof installations to nonprofits, affordable housing, and select cooperatively-owned housing. Privately-owned buildings can receive installations at minimal cost. The initiative also provides local job-seekers with training and paid work experience coating rooftops. The following map shows the locations of cool roofs installed by the program and reported by building owners from 2009 – 2019. Since the program’s inception over 10 million square feet of Cool Roofs have been installed in NYC. As part of Cool Neighborhoods initiative, since 2017, the City targets outreach and prioritizes installations in the most heat-vulnerable neighborhoods using the Heat Vulnerability Index.
The New York City Department of Housing Preservation and Development (HPD) has developed New York City Green Housing Preservation Program, a program to help building owners retrofit with higher-performance materials, which would reduce the amount of energy and water used in building operations. This program provides tax credits, rebates, and incentives that promote energy efficiency, and offers tips on how to lower energy bills.
Utilities contribute to this effort by offering demand-reduction programs — incentives to commercial and industrial building owners to permanently reduce their energy consumption. Con Edison offers a number of energy efficiency tools to encourage residential, small business, multifamily building, and commercial/industrial customers to reduce energy consumption.
Actions taken by New York City to reduce the amount of greenhouse gas emissions serve the long-term goal of slowing the rate of climate change. Taking action to increase the energy efficiency of New York City buildings has a more immediate impact — to avoid power outages during periods of extended heat and reduce building electricity costs.
Natural Cover and Green Areas
Certain features of New York City’s natural environment can partially offset the impact of extreme heat upon different neighborhoods. The urban heat-island effect is directly tied to a neighborhood’s ratio of ground covered by natural vegetation to that covered by asphalt and other artificially built, impervious surfaces. Trees and vegetation naturally cool the surrounding air by releasing moisture and absorbing carbon dioxide from the atmosphere; by contrast, many built surfaces trap heat and keep the surrounding environment warmer. Planting trees and vegetation along streets and in open spaces serves as ecological infrastructure in New York City and can significantly reduce local air temperatures. Replacing concrete, asphalt, or even grassy surfaces with trees can reduce the local air temperature by several degrees. Green roofs – roofs with vegetation planted on them – can reduce both outdoor and indoor air temperatures.
In response to rising temperatures due to climate change, the New York City Mayor’s Office launched the Cool Neighborhoods NYC initiative in June 2017. As of June 2023, the initiative has led to the planting of 13,154 trees citywide, aiming for a total of 14,900 by the end of the month. This effort represents the highest tree planting total in six fiscal years and shows a continued upward trend in tree planting across the five boroughs.
A significant focus of the planting has been on neighborhoods identified as heat vulnerable by the NYC Heat Vulnerability Index (HVI). More than 5,700 new plantings in FY23 are in these HVI neighborhoods, which include areas in Bronx, Brooklyn, Manhattan, and Queens. Since 2017, a total of 15,677 trees have been planted in the most vulnerable neighborhoods (HVI-5), with an estimated 9,700 more planned through Spring 2024. With an additional $136 million funding from the Adams administration, the goal is to plant trees in every viable location in HVI-4 and HVI-5 neighborhoods by 2026.
The New York City Department of Parks and Recreation (NYC Parks) actively maintains over 800,000 mapped trees, including 650,000 street trees and more than 150,000 park trees. In December 2022, the NYC Tree Map was introduced, providing a digital platform for New Yorkers to interact with and learn about nearly one million individually managed city trees in real-time.
The City’s Green Infrastructure Program, led by New York City’s Department of Environmental Protection, promotes a variety of sustainable green infrastructure practices, including green roofs, rain gardens, and right-of-way bioswales on City-owned property such as streets, sidewalks, schools, and public housing. Although this program’s goal is primarily to reduce the impacts of stormwater runoff and combined sewer overflows, its green-roof and other strategies also help to reduce the urban heat island effect in New York City.
 New York City Department of Health and Mental Hygiene. “Heat Illness and Heat Waves.” http://www.nyc.gov/html/doh/html/environmental/heat-illness.html.
 Weather Underground. “Central Park, NY.” Weather Underground. https://www.wunderground.com/history/monthly/us/ny/central-park/KNYC/date/2018-9.
 WebMD. “Fitness and Exercise: Heat Exhaustion.” WebMD. http://www.webmd.com/fitness-exercise/heat-exhaustion.
 National Weather Service. “National Weather Service New York, NY Excessive Heat Page.” National Weather Services: National Oceanic and Atmospheric Administration. https://www.weather.gov/okx/excessiveheat.
 National Weather Service, Office of Climate, Water, and Weather Statistics. “Natural Hazard Statistics: Weather Fatalities 2017.” National Weather Service: National Oceanic and Atmospheric Administration. http://www.nws.noaa.gov/om/hazstats.shtml.
 Lin S., et al. “Extreme High Temperatures and Hospital Admissions for Respiratory and Cardiovascular Diseases.” Epidemiology, 20(2009): 738-746.
 U.S. Department of Energy. “Air Sealing Your Home.” Energy.gov. https://www.energy.gov/energysaver/weatherize/air-sealing-your-home.