Published: March 26, 2020
The number in each state depicts the average annual number of tornadoes based on the 20-year period from 1991 to 2010.
Tornadoes can occur in any month of the year across the United States, and it should come as no surprise that the Plains states have the highest frequency of twisters in an average year.
NOAA's National Centers for Environmental Information (NCEI) compiled the 20-year annual average for every state based on data from 1991 to 2010. The NCEI data have been illustrated on the map at the top of this article.
The number in each state depicts the average annual number of tornadoes, with various colors representing higher and lower averages.
States shaded in green in the Northeast and parts of the West each have five or fewer tornadoes in a typical year.
The yellow-shaded states in the mid-Atlantic, Great Lakes, Ohio Valley, mid-South, parts of the Southeast, as well as Montana, Wyoming, New Mexico and California, typically have between 10 and 30 tornadoes in an average year.
States shaded in orange in portions of the South, Mississippi Valley and Northern Plains have 31 to 45 tornadoes per year, on average.
The red-shaded states, including Florida, Illinois, Iowa, Nebraska, Oklahoma and Colorado, typically have between 51 and 66 tornadoes annually.
The two most active states for tornadoes are Texas, with 155, and Kansas, with 96, in an average year. They are both located in the heart of Tornado Alley, a nickname given to an area in the Plains between Central Texas and South Dakota that has some of the most tornadic activity in the world.
As a whole, the U.S. averaged 1,225 tornadoes annually from 1999 to 2018, 54% of which occurred between April and June.
When and Where the Most Tornadoes Typically Occur
April kicks off what is typically the most active and dangerous three-month period of the year for tornadoes in the United States.
Although strong tornadoes can occur in any month, weather history shows that April, May and June are the months with the highest potential of having both the greatest number of tornadoes and the most intense tornadoes in a given year.
May typically has the most tornadoes each year, with an average of 272. This is followed by June and April, which average 202 and 189 tornadoes per year, respectively.
The three-month period from April through June averages the most number of tornadoes during the year.
Historically, the highest threat of tornadoes migrates from the South into parts of the Plains and Midwest as we advance through April, May and June.
For example, the potential for tornadoes in the South is much lower in June compared to April. Although moisture is abundant across the southern U.S. in late spring, the strong jet stream winds needed to make conditions favorable for tornadic thunderstorms move northward toward the Canadian border.
By the summer, tornadoes can occur virtually anywhere nationwide because warmth and humidity are the most widespread of any time of the year.
A secondary peak in tornado activity occurs in the fall in the Gulf Coast states, but this activity can sometimes spread northward to the Ohio Valley and southern Great Lakes.
From late fall through the winter, the greatest chance of tornadoes moves back to the South with the warmest air and much of the moisture.
Click through the slideshow below to see where the average tornado risk area is during each month.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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