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Facts + Statistics: Tornadoes and thunderstorms

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Convective storms

Convective storms result from warm, moist air rising from the earth, and depending on atmospheric conditions, may develop into tornadoes, hail, thunderstorms with lightning, or straight-line winds. Convective storms are the most common and damaging natural catastrophes in the United States, according to Triple-I’s May 2020 white paper, Severe convective storms: Evolving risks call for innovation to reduce costs, drive resilience.

Tornadoes

A tornado is a violently rotating column of air that extends from a thunderstorm and comes into contact with the ground, according to the National Oceanic and Atmospheric Administration (NOAA). In an average year, about 1,000 tornadoes are reported nationwide, according to NOAA. Tornado intensity is measured by the enhanced Fujita (EF) scale. The scale rates tornadoes on a scale of 0 through 5, based on the amount and type of wind damage. It incorporates 28 different damage indicators, based on damage to a wide variety of structures ranging from trees to shopping malls.

The Fujita Scale For Tornadoes

Ìý Ìý Original F scale (1) Enhanced F scale (2)
Category Damage Wind speed (mph) 3-second gust (mph)
F-0 Light 40-72Ìý 65-85
F-1 Moderate 73-112 86-110
F-2 Considerable 113-157 111-135
F-3 Severe 158-207 136-165
F-4 Devastating 208-260 166-200
F-5 Incredible 261-318 Over 200

(1) Original scale: wind speeds represent fastest estimated speeds over one quarter of a mile.
(2) Enhanced scale: wind speeds represent maximum 3-second gusts.

Source: U.S. Department of Commerce, National Oceanic and Atmospheric Administration.

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View Archived Graphs

Top 10 Costliest U.S. Catastrophes Involving Tornadoes (1)

($ millions)

Ìý Ìý Ìý Ìý Estimated insured loss
Rank Date Event Location Dollars when
occurred		 In 2024 dollars (2)
1 Aug. 8-12, 2020 Midwest Derecho IA, IL, IN, KS, MI, MN, MO, NE, OH, SD,
WI, PA, DC, MD, VA, WV		 $9,200 $11,158
2 Apr. 22-28, 2011 Tornado Outbreak AL, AR, GA, IL, KY, LA, MO, MS, OH,
OK, TN, TX, VA		 7,560 10,611
3 May 21-27, 2011 Joplin, MO Tornado AR, GA, IA, IL, IN, KS, KY, MI, MN, MO,
NC, NE, NY, OH, OK, PA, TN, TX, VA, WI		 7,000 9,779
4 May 2-11, 2003 SCS Outbreak AL, AR, CO, GA, IA, IL, IN, KS, KY, MO,
MS, NC, NE, OH, OK, SC, SD, TN		 3,300 5,677
5 May 6-10, 2024 SCS Outbreak AL, AR, CO, FL, GA, IL, IN, KS, KY, LA, MI,
MO, MS, NC, OH, OK, SC, TN, TX, WI		 5,200 5,200
6 Mar. 1-3, 2023 SCS Outbreak AL, AR, GA, IN, KY, MS, OH, PA, TN, VA 4,900 5,125
7 Mar. 12-16, 2024 SCS Outbreak AR, IL, IN, KS, KY, MO, MS, OH, OK, TX 4,800 4,800
8 May 27-30, 2019 SCS Outbreak AR, CO, IA, IL, IN, KS, MO, NJ, NY, OH,
OK, PA, TX, WV, WY		 3,650 4,499
9 Mar. 31 - Apr. 1, 2023 Tornado Outbreak AL, AR, DE, GA, IL, IN, IO, KY, MI, NE,
OH, PA, TN, TX		 4,300 4,497
10 Jun. 21-26, 2023 SCS Outbreak CO, TX, Southeast 4,250 4,397

(1) Defined by Aon as severe convective storms including insured thunderstorm events and may include tornado, hail, damaging straight-line winds (derechos) and flash flood impacts from events. Subject to change as loss estimates are further developed. As of January 2025.
(2) Adjusted for inflation by Aon using the U.S. Consumer Price Index.

Source: Aon.

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Top 10 States, By Number Of Tornadoes, 2024 (1)

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Rank State Number of tornadoes (2) Fatalities
1 Texas 169 9
2 Iowa 131 6
2 Nebraska 131 0
4 Illinois 126 0
5 Missouri 105 1
6 Florida 103 8
7 Louisiana 92 3
8 Oklahoma 91 8
9 Kansas 89 1
10 Ohio 82 3

(1) Numbers include preliminary estimates as of January 2025.
(2) Excludes Puerto Rico. Tornadoes that cross state lines are counted in every state in which they touch down.

Source: U.S. Department of Commerce, Storm Prediction Center, National Weather Service.

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Tornadoes And Related Deaths By State, 2024 (1)

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State Tornadoes Fatalities Rank (2) State Tornadoes Fatalities Rank (2)
Alabama 79 1 12 Montana 4 0 35
Alaska 0 0 (3) Nebraska