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.

Tornadoes accounted for 40 percent of inflation-adjusted insured catastrophe losses from 1997 to 2016, according to Property Claim Services (PCS®), a Verisk Analytics® business. In 2016 insured losses from U.S. tornadoes/thunderstorms totaled $14 billion, up from $9.6 billion in 2015. The number of tornadoes rose to 1,406 in 2017 from 971 in 2016, according to the National Oceanic and Atmospheric Administration (NOAA). The 2017 total was the highest since 2011, when there were 1,691 tornadoes, including two spring events that resulted in over $14 billion in losses when they occurred. There were 35 direct fatalities from tornadoes in 2017, up from 18 in 2016, according to NOAA. May was the top month for tornadoes in 2016, with 287 twisters. The United States experiences more tornadoes than any other country, according to a 2013 report by Lloyd’s of London.

Insured Losses

The United States experiences more tornadoes than any other country. Tornadoes accounted for 39.9 percent of insured catastrophe losses from 1997 to 2016, according to Verisk’s Property Claim Services (PCS). A March 2017 report by Willis Re found that the average annual loss from severe convective storms is $11.23 billion (in 2016 dollars) compared to $11.28 billion from hurricanes, based on PCS data. In 2016 insured losses from U.S. tornadoes/thunderstorms totaled $14 billion, up from $9.6 billion in 2015. 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 $7.9 billion in insured damages (in 2016 dollars). That event was the 10th costliest U.S. catastrophe, based on insured losses, according to PCS. The second costliest catastrophe involving tornadoes, based on insured losses, struck Joplin, Missouri, and other locations in May 2011. The catastrophe cost $7.4 billion in insured losses in 2016 dollars. (See chart below.) The National Weather Service posts updated information on tornadoes.

Natural Catastrophe Losses In The United States, 2016

(Based on perils)

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Number Of Tornadoes And Related Deaths Per Month, 2017 (1)

num_of_torn_and_rel_deaths_per_month_17.gif

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

($ millions)

			Estimated insured loss (2)
Rank	Date	Location	Dollars when occurred	In 2016 dollars (3)
1	Apr. 22-28, 2011	AL, AR, GA, IL, KY, LA, MO, MS, OH, OK, TN, TX, VA	$7,300	$7,875
2	May 20-27, 2011	AR, GA, IA, IL, IN, KS, KY, MI, MN, MO, NC, NE, NY, OH, OK, PA, TN, TX, VA, WI	6,900	7,443
3	May 2-11, 2003	AL, AR, CO, GA, IA, IL, IN, KS, KY, MO, MS, NC, NE, OH, OK, SC, SD, TN	3,205	4,118
4	Oct. 4-6, 2010	AZ	2,700	2,973
5	Apr. 6-12, 2001	AR, CO, IA, IL, IN, KS, KY, MI, MN, MO, NE, OH, OK, PA, TX, WI	2,200	2,927
6	Mar. 2-3, 2012	AL, GA, IN, KY, OH, TN	2,500	2,648
7	Apr. 28-29, 2012	IL, IN, KY, MO, TX	2,500	2,648
8	May 12-16, 2010	IL, MD, OK, PA, TX	2,000	2,202
9	Apr. 27-May 3, 2002	AR, GA, IL, IN, KS, KY, MD, MO, MS, NC, NY, OH, PA, TN, TX, VA, WV	1,675	2,195
10	Apr. 13-15, 2006	IA, IL, IN, WI	1,850	2,175

(1) Based on data through May 30, 2017.
(2) Property coverage only. In addition to losses due to tornadoes themselves, amounts may include losses due to hail, wind and flooding during the same event.
(3) Adjusted for inflation through 2016 by ISO using the GDP implicit price deflator.

Source: The Property Claim Services® (PCS®) unit of ISO®, a Verisk Analytics® company.

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Top 10 States, By Number Of Tornadoes, 2017 (1)

Rank	State	Number of tornadoes	Fatalities
1	Texas	176	4
2	Georgia	131	16
3	Missouri	102	1
4	Louisiana	88	3
5	Mississippi	81	5
6	Kansas	74	0
7	Alabama	65	0
8	Illinois	65	3
9	Oklahoma	62	1
10	Iowa	57	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, 2017 (1)

State	Tornadoes	Fatalities	Rank (2)	State	Tornadoes	Fatalities	Rank (2)
Alabama	65	0	7	Montana	2	0	37
Alaska	0	0	(3)	Nebraska	38	0	16
Arizona	3	0	34	Nevada	0	0	(3)
Arkansas	26	0	22	New Hampshire	0	0	(3)
California	2	0	37	New Jersey	2	0	37
Colorado	20	0	26	New Mexico	11	0	29
Connecticut	0	0	(3)	New York	12	0	28
Delaware	1	0	41	North Carolina	34	0	19
D.C.	1	0	41	North Dakota	41	0	15
Florida	41	0	13	Ohio	43	0	12
Georgia	131	16	2	Oklahoma	62	1	9
Hawaii	0	0	(3)	Oregon	3	0	34
Idaho	1	0	41	Pennsylvania	26	0	22
Illinois	65	3	7	Rhode Island	0	0	(3)
Indiana	36	0	17	South Carolina	51	1	11
Iowa	57	0	10	South Dakota	21	0	25
Kansas	74	0	6	Tennessee	35	0	18
Kentucky	29	0	20	Texas	176	4	1
Louisiana	88	3	4	Utah	0	0	(3)
Maine	10	0	31	Vermont	0	0	(3)
Maryland	4	0	33	Virginia	23	0	24
Massachusetts	2	0	37	Washington	3	0	34
Michigan	11	0	29	West Virginia	5	0	32
Minnesota	41	0	13	Wisconsin	28	1	21
Mississippi	81	5	5	Wyoming	15	0	27
Missouri	102	1	3	United States	1,522	35

(1) Ranked by total number of tornadoes.
(2) States with the same number receive the same ranking.
(3) State had no tornadoes in 2017.
(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, 1998-2017 (1)

Year	Tornadoes	Deaths	Year	Tornadoes	Deaths
1998	1,424	130	2008	1,692	126
1999	1,345	94	2009	1,156	21
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	971	18
2007	1,098	81	2017	1,406	35