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)

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Natural Catastrophe Losses In The United States, 2019

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

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(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