Facts + Statistics: Tornadoes and thunderstorms

Convective storms

Convective storms are the result of 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 the Triple-I’s May 2020 white paper, Severe convective storms.

According to catastrophe modeling company RMS, insured losses in the United States from these storms average about $17 billion each year, nearly equal to the losses incurred by hurricanes. While scientists cannot say that these storms are increasing, given the relatively short periods of reliable, post-Doppler radar data, it is clear that the losses are increasing, as a result of population growth and economic development. In addition, the geographic span of these storms appear to be changing from what previously was called the “tornado alley” to the southern United States with tornado formation tending to develop further east.

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

    Original F scale (1) Enhanced F scale (2)
Category Damage Wind speed (mph) 3-second gust (mph)
F-0 Light 40-72  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.

2021 Tornadoes: In 2021, there were there were 1,376 tornadoes in the United States, compared with 1,075 in 2020, according to preliminary data from the National Oceanic and Atmospheric Administration (NOAA). Tornadoes killed over 100 people in 2021, including about 90 in the December 10 series of tornadoes. In 2020, 76 people perished in tornadoes.

 

 

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The following chart shows the top 10 catastrophes involving tornadoes. It counts severe convective storms that may include tornadoes and other perils such as straight-line winds (derechos) and hail. The costliest U.S. catastrophe involving tornadoes occurred in August 2020 during a multi-day outbreak that included the August 10 Midwest Deracho causing $9.6 billion in insured losses in 2021 dollars.

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

($ millions)

        Estimated insured loss
Rank Date Event Location Dollars when occurred In 2021 dollars (2)
1 Aug. 8-12, 2020 Includes Aug. 10 Midwest Derecho IA, IL, IN, KS, MI, MN, MO, NE, OH, SD, WI, PA, DC, MD, VA, WV $9,200 $9,580
2 Apr. 22-28, 2011 Late April 2011 Super Tornado Outbreak AL, AR, GA, IL, KY, LA, MO, MS, OH, OK, TN, TX, VA 7,300 8,800
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 6,900 8,270
4 May 2-5, 2003   AL, AR, CO, GA, IA, IL, IN, KS, KY, MO, MS, NC, NE, OH, OK, SC, SD, TN 3,205 4,730
5 Dec. 10-12, 2021   AR, IL, IN, KY, MI, MO, NY, OH, TN, TX 4,000 4,000
6 May 27-30, 2019   CO, TX, OK, KS, AR, MO, IA, IL, IN,
OH, PA, WV, WY, NJ, NY
3,650 3,860
7 Apr. 10-15, 2016 San Antonio Hailstorm TX, LA, OK, AR, MS, KS, MO 3,200 3,620
8 Apr. 6-12, 2001 St. Louis Hailstorm AR, CO, IA, IL, IN, KS, MI, MN, MO, NE, OH, OK, PA, TX 2,200 3,370
9 May 18-23, 2014   CO, DE, IA, IL, IN, MT, NY, OH, PA,
SC, VA
2,950 3,360
10 Oct. 5-6, 2010 Phoenix Hailstorm AZ 2,700 3,350

(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. Includes events that occurred through 2020. Subject to change as loss estimates are further developed. As of February 1, 2022.
(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, 2021 (1)

 

Rank State Number of tornadoes Fatalities
1 Texas 118 1
2 Alabama 100 7
3 Mississippi 92 1
4 Illinois 80 6
5 Iowa 70 0
6 Tennessee 66 4
7 Georgia 57 0
7 Kentucky 57 73
8 Nebraska 53 0
9 Louisiana 50 1
9 Missouri 50 2
10 Colorado 48 0

(1) 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, 2021 (1)

 

State Tornadoes Fatalities Rank (2) State Tornadoes Fatalities Rank (2)
Alabama 100 7 2 Montana 1 0 34
Alaska 0 0 (3) Nebraska 53 0 8
Arizona 6 0 29 Nevada 3 0 32
Arkansas 41 2 13 New Hampshire 0 0 (3)
California 5 0 30 New Jersey 13 0 24
Colorado 48 0 10 New Mexico 18 0 21
Connecticut 8 0 27 New York 14 0 23
Delaware 2 0 33 North Carolina 19 3 20
D.C. 2 0 33 North Dakota 21 0 21
Florida 32 0 16 Ohio 37 0 15
Georgia 57 0 7 Oklahoma 39 0 14
Hawaii 0 0 (3) Oregon 0 0 (3)
Idaho 0 0 (3) Pennsylvania 44 1 12
Illinois 80 6 4 Rhode Island 2 0 33
Indiana 19 0 20 South Carolina 24 0 18
Iowa 70 0 5 South Dakota 19 0 20
Kansas 46 0 11 Tennessee 66 4 6
Kentucky 57 73 7 Texas 118 1 1
Louisiana 50 1 9 Utah 4 0 31
Maine 0 0 (3) Vermont 2 0 33
Maryland 11 0 25 Virginia 9 0 26
Massachusetts 7 0 28 Washington 2 0 33
Michigan 17 0 22 West Virginia 2 0 33
Minnesota 37 0 15 Wisconsin 28 0 17
Mississippi 92 1 3 Wyoming 2 0 33
Missouri 50 2 9 United States (4) 1,377 101  

(1) Ranked by total number of tornadoes.
(2) States with the same number of tornadoes receive the same ranking.
(3) State had no tornadoes in 2021.
(4) The U.S. total will not match data used in other charts because it counts tornadoes that cross state lines.

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

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Tornadoes And Related Deaths In The United States, 2002-2021 (1)

 

Year Tornadoes Deaths Year Tornadoes Deaths
2002 941 55 2012 938 70
2003 1,376 54 2013 906 55
2004 1,819 36 2014 886 47
2005 1,264 38 2015 1,177 36
2006 1,103 67 2016 976 18
2007 1,098 81 2017 1,429 35
2008 1,692 126 2018 1,126 10
2009 1,156 21 2019 1,517 42
2010 1,282 45 2020 1,075 76
2011 1,691 553 2021 1,376 101

(1) Excludes Puerto Rico. A tornado that crosses state lines counts as one event.

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

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U.S. Tornado Count, 2021

 

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

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