A severe thunderstorm produces wind gusts of 58 mph or more and/or hailstones of 1 inch or more in diameter.

Hailstone size varies widely, and the size correlates with the severity of the thunderstorm.

Hail Size and Related Damages

Source: Burt, Extreme Weather, 2007

Severe thunderstorms can also produce tornadoes. Prior to 2007, the NWS used the Fujita Scale (F-Scale) as the standard measurement to rate the strength of a tornado. Since February 1, 2007, NWS uses the Enhanced Fujita Scale (EF-Scale) as its standard measurement.

The EF-scale is more complex than the F-Scale and enables surveyors to assess tornado severity with greater precision. However, the F-Scale is still used to place the more recent high-wind events into the historical context.

NOAA’s chart compares these two scales and indicates the severity of damage associated with these rankings.

Enhanced Fujita Scale

F-Scale	3-sec. gust speed (mph)	EF-Scale	3-sec. gust speed (mph)	Typical Damage
F0	45-78	EF0	65-85	Light damage. Some damage to chimneys. Branches broken off trees. Shallow-rooted trees pushed over, signboards damaged.
F1	79-117	EF1	89-109	Moderate damage. Peels surface off roofs. Mobile homes pushed off foundations or overturned. Moving autos blown off roads.
F2	118-161	EF2	110-137	Considerable damage. Roofs torn off frame houses. Mobile homes demolished. Boxcars overturned. Large trees snapped or uprooted. Light-object missiles generated. Cars lifted off ground.
F3	162-209	EF3	138-167	Severe damage. Roofs and some walls from off well-constructed houses. Trains overturned. Most trees in forest uprooted. Heavy cars lifted off the ground and thrown.
F4	210-261	EF4	168-199	Devastating damage. Well-constructed houses leveled. Structures with weak foundations blown away some distance. Cars thrown and large missiles generated.
F5	262-317	EF5	200-234	Incredible damage. Strong frame houses leveled off foundations and swept away. Automobile-sized missiles fly through the air in excess of 100 meters (109 yards). Trees debarked. Incredible phenomena will occur.

 

Source: NOAA

The Beaufort Wind Scale is used to associate observations made during wind events with different levels of wind force and speed.

Beaufort Wind Scale

Force	Wind Speed (mph)	Terminology	Description
0	Less than 1	Calm	Calm, smoke rises vertically
1	1 - 4	Light air	Smoke drift indicates wind direction, still wind vanes
2	5 - 7	Light breeze	Wind felt on face, leaves rustle, vanes begin to move
3	8 - 12	Gentle breeze	Leaves and small twigs constantly moving, light flags extended
4	13 - 18	Moderate breeze	Dust, leaves, and loose paper lifted, small tree branches move
5	20 - 24	Fresh breeze	Small trees in leaf begin to sway
6	25 – 31	Strong breeze	Large branches in motion; whistling in telephone wires; umbrellas used with difficulty
7	32 – 38	Near gale	Whole trees in motion; resistance felt while walking against the wind
8	39 - 46	Gale	Twigs break off trees; wind impedes walking
9	47 – 54	Strong gale	Slight structural damage to chimneys and slate roofs
10	55 - 63	Storm	Seldom felt inland; trees uprooted; considerable structural damage
11	64 - 72	Violent storm	Very rarely experienced; widespread structural damage; roofing peels off buildings; windows broken; mobile homes overturned
12	73+	Hurricane	Widespread structural damage; roofs torn off homes; weak buildings and mobile homes destroyed; large trees uprooted

 

Source: NOAA, 2013

New York City estimates the probability of future high-wind events based upon the annual frequency of past severe thunderstorms. From 2000 to 2017, New York City’s Hazard History and Consequence Database indicates that the city has had 209 severe weather events, including events where there were high winds, hailstones, lightning, macrobursts, and tornadoes. Of the 209 severe weather events tallied in the Hazard History and Consequence Database, 24 events produced hailstones ranging from 0.25 inches to 2.75 inches in diameter. Generally, the reported hailstone size was small, but 15 events produced hailstones of more than 0.75 inches in diameter.

The probability of future severe storms and damaging winds in New York City is high and such events may happens multiple times on a local scale each year. By comparison, the recurrence interval for tornadoes and large hail in New York City is much lower.

Tornadoes in New York City are less common than severe thunderstorms, but they are still likely to occur in the future.

New York City’s first reported tornado was in 1974.Over the past 40 years, twelve tornadoes appeared in New York City, with eleven ranked at low severity levels of F0 or F1.

Reports of tornadoes have increased in New York City over the years. Seven tornadoes have been reported between 2007 and 2018, compared with only six reported in the previous 33 years. This increase in reported occurrences may be due to the greater precision of the Enhanced Fujita Scale.

Non-thunderstorm high-wind events happen very frequently in New York City -- including tropical cyclones, nor’easters, atmospheric conditions forcing air from high- to low-pressure areas, and interactions between strong cold and warm frontal systems.

Based on the historical record, New York City experiences at least one of these high-wind events per year.

Thunderstorms occur throughout New York City, but they do not necessarily affect all five boroughs simultaneously or produce high winds or hail that affect every location with the same severity. Some thunderstorms and their associated wind and hailstorms are extremely localized events.

A common misconception is that tornadoes do not occur in dense urban areas such as New York City. Scientists say that although tornadoes are rare, they could occur in any part of the city.

Since 1950, at least one tornado has occurred in each of the five boroughs, as shown on this map. Note that Manhattan’s August 1995 tornado is not plotted because accurate coordinates for this event are unavailable.