Facts + Statistics: Tornadoes and thunderstorms

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 U.S. experiences more tornadoes than any other country in the world, according to a 2013 report by Lloyd’s of London. (See Executive Summary, page 4 of Tornadoes a Rising Risk? for additional findings and statistics.)

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.

2020 Tornadoes: In 2020 there were 1,075 tornadoes compared with 1,517 in 2019, according to preliminary estimates from the National Oceanic and Atmospheric Administration (NOAA). In 2020 about 76 people perished in tornadoes compared with 42 in 2019. On April 12 and 13, 30 people perished in tornadoes in Georgia, Mississippi, South Carolina and Tennessee. On March 2 and 3, 25 people were killed in tornadoes in central Tennessee, including the city of Nashville. Tornado deaths in 2020 were the highest since 2011, when 553 people were killed in 1,691 tornadoes.

2019 Tornadoes: The number of tornadoes rose to 1,517 in 2019 from 1,126 in 2018, according to NOAA. The 2019 total was the highest since 2011, when there were 1,691 tornadoes. There were 42 direct fatalities from tornadoes in 2019, compared with 10 in 2018, according to NOAA. May was the top month for tornadoes in 2019, with 510 twisters, including a system occurring May 27 to May 30 that resulted in $3.7 billion in insured losses, according to Aon. March was the deadliest month in 2019—on March 3 an F4 tornado struck Alabama and killed 23 people and left a half-mile wide path of destruction. The March 3 tornado storm system was the deadliest outbreak in the United States since a system in Arkansas and Mississippi in April 2014 killed 35 people.

Insured Losses

Convective storms are the most common and damaging natural catastrophes in the United States, according to the Insurance Information Institute’s May 2020 white paper, Severe convective storms. According to Aon, insured losses in the United States from these storms totaled at least $10 billion each year since 2008. While scientists cannot say that these storms are increasing, it is clear that the losses are increasing, as a result of population growth and economic development. In addition, the geography, frequency and intensity of these storms also may be changing. Aon reports that there were 14 separate billion-dollar economic, or total loss severe convective events in 2020. The most expensive included the August 10 Midwest derecho, or straight lines winds. Aon’s current estimate of insured losses for severe convective storms in 2020 is a record $36 billion. The previous record was $32 billion in 2011.

The United States experiences more tornadoes than any other country. The National Oceanic and Atmospheric Administration notes that tornadoes can happen any time of year. The costliest U.S. catastrophe involving tornadoes, based on insured losses, occurred in April 2011. It hit Tuscaloosa, Alabama, and other areas, and cost $8.5 billion in insured damages (in 2020 dollars). The second costliest was the tornado system from August 8 to 12, 2020 that included the August 10 Midwest Derecho that caused $8.3 billion in insured losses.. (See chart below.) The National Weather Service posts updated information on tornadoes.

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, it is clear that the losses are increasing, as a result of population growth and economic development. In addition, the geography, frequency and intensity of these storms also may be changing.

According to Aon, there were 14 separate billion-dollar economic, or total loss, severe convective events in 2020. The most expensive included the August 10 Midwest derecho (straight line winds).

Natural Catastrophe Losses In The United States, 2019

(Based on perils; US$ millions)

Source: © 2020 Munich Re, NatCatSERVICE; Property Claim Services (PCS®)*, a Verisk Analytics® business. As of June 2020.

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Number Of Tornadoes And Related Deaths Per Month, 2019 (1)

 

(1) Excludes Puerto Rico. A tornado that crosses state lines is counted as a single event in this chart.

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

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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 August 10, 2020, Midwest Derecho, which is included in the chart as part of the August 8-12, 2020 outbreak, would rank as the fourth-costliest insured severe convective storm event on record for the U.S. if considered alone. It caused $7 billion in insured losses in Iowa, Illinois Wisconsin and Indiana.

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

($ millions)

        Estimated insured loss
Rank Date Event Location Dollars when occurred In 2020 dollars (2)
1 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 $8,490
2 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 8,250 8,250
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 7,990
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 4,570
5 May 27-30, 2019   CO, TX, OK, KS, AR, MO, IA, IL, IN, OH, PA, WV, WY, NJ, NY 3,650 3,730
6 Apr. 10-15, 2016 San Antonio Hailstorm TX, LA, OK, AR, MS, KS, MO 3,200 3,500
7 Apr. 6-12, 2001 St. Louis Hailstorm AR, CO, IA, IL, IN, KS, MI, MN, MO, NE, OH, OK, PA, TX 2,200 3,250
8 May 18-23, 2014   CO, DE, IA, IL, IN, MT, NY, OH, PA,
SC, VA
2,950 3,240
9 Oct. 5-6, 2010 Phoenix Hailstorm AZ 2,700 3,230
10 Mar. 2-3, 2012   AL, GA, IN, KY, OH, TN 2,500 2,850

(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 23, 2021.
(2) Adjusted for inflation by Aon using the U.S. Consumer Price Index.

Source: Aon.

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  • The costliest U.S. catastrophe involving tornadoes occurred in April 2011, when a spate of twisters hit Tuscaloosa, Alabama, and other areas, causing $8.5 billion in insured losses in 2020 dollars.
  • The second costliest was the tornado system from August 8 to 12, 2020 that included the August 10 Midwest Derecho that caused $8.3 billion in insured losses.

Top 10 States, By Number Of Tornadoes, 2019 (1)

 

Rank State Number of tornadoes Fatalities
1 Texas 188 2
2 Mississippi 138 2
3 Kansas 127 0
4 Oklahoma 99 4
5 Missouri 98 3
6 Louisiana 97 3
7 Alabama 95 25
8 Georgia 60 0
9 North Carolina 59 0
10 Ohio 59 1

(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, 2019 (1)

 

State Tornadoes Fatalities Rank (2) State Tornadoes Fatalities Rank (2)
Alabama 95 25 7 Montana 6 0 32
Alaska 0 0 (3) Nebraska 44 0 14
Arizona 10 0 30 Nevada 1 0 41
Arkansas 31 0 19 New Hampshire 0 0 (3)
California 16 0 27 New Jersey 9 0 31
Colorado 53 0 12 New Mexico 21 0 25
Connecticut 1 0 41 New York 4 0 36
Delaware 1 0 41 North Carolina 59 0 9
D.C. 0 0 (3) North Dakota 14 0 29
Florida 25 0 22 Ohio 59 1 9
Georgia 60 0 8 Oklahoma 99 0 4
Hawaii 0 0 (3) Oregon 4 4 36
Idaho 5 0 35 Pennsylvania 34 0 17
Illinois 37 0 16 Rhode Island 1 0 41
Indiana 39 0 15 South Carolina 18 0 26
Iowa 53 1 12 South Dakota 23 0 24
Kansas 127 0 3 Tennessee 16 0 27
Kentucky 28 0 21 Texas 188 2 1
Louisiana 97 3 6 Utah 0 0 (3)
Maine 1 0 41 Vermont 1 0 41
Maryland 6 0 32 Virginia 24 0 23
Massachusetts 3 0 38 Washington 2 0 40
Michigan 6 0 32 West Virginia 3 0 38
Minnesota 54 0 11 Wisconsin 32 0 18
Mississippi 138 2 2 Wyoming 30 0 20
Missouri 98 3 5 United States (4) 1,676 41  

(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 2019.
(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, 2000-2019 (1)

Year Tornadoes Deaths Year Tornadoes Deaths
2000 1,071 40 2010 1,282 45
2001 1,216 40 2011 1,691 553
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 1,520 41

(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, 2019

 

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

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Convective Storm Events* in the U.S., 1980-2018

(Overall and insured losses)

Source: © 2019 Munich Re, Geo Risks Research, NatCatSERVICE. As of March 2019. 

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Convective Storm Events* in the U.S., 1980-2018

(Overall losses: nominal, inflation adjusted, and normalized)

Source: © 2019 Munich Re, Geo Risks Research, NatCatSERVICE. As of March 2019. 

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