May Is The Most Active Month For Tornadoes In the US, But Not All Years Deliver On This Expectation

Which Month Typically Sees The Most Tornadoes?

Tornado Alley and May are often mentioned together in the same sentence, and for good reason, since the month produces the most twisters annually and the epicenter is focused in that general region of the central United States.

But as recent years have shown, not every May lives up to this expectation.

Big Picture

-Greatest Tornado Threat Shifts, Expands: Tornadoes are possible across a broad portion of the nation in May, from the Plains to the East Coast. But the greater risk of tornadic storms is in portions of the Plains and Midwest. That's a change from earlier in spring, when the greater risk of tornadoes is usually in the Deep South and sometimes the Midwest.

-It Has The Highest Average Number Of Twisters: In the 20 years ending with 2023, May averaged 260 tornadoes annually. That's higher than April and June which, on average, are the second- (202) and third-busiest (186) months for twisters, respectively.

Deeper Dive

-Tornado Intensity Matters, Too: May, along with April, is in the heart of spring when violent tornadoes (EF4 to EF5 damage) are more likely than any time of year. Higher-end tornadoes like these, as well as those rated EF2 and EF3, contribute to an overwhelming majority of tornado deaths.

Nine of the 25 deadliest U.S. tornadoes in history have occurred in May, based on estimates from NOAA's Storm Prediction Center. That's the most of any month, with April and June just behind with seven each.

Going back even farther, May 2019 had 510 tornadoes compared to just 126 in May 2020.

So as you can see, the average of 260 in the month is a mix of some higher years, some lower ones, and some right on par with expectations.

More To Know

-The Ideal Setup For May Tornadoes: May is when Gulf moisture is drawn farther north most successfully by strong low-pressure systems when compared to earlier in spring. At the same time, a larger area of the country can heat into the 70s, 80s and 90s for greater thunderstorm development.

The jet stream is also still strong enough and spreads out of the West into the nation's midsection to create strong wind shear over the Plains. That wind shear causes storms to spin, which in turn can help some of them generate tornadoes.

-What Causes Less Active Mays: The jet stream mentioned above is an important player – specifically, what configuration it takes much of the month. If the dominant weather pattern has the jet stream dipping southward in the eastern states, then that keeps temperatures cooler and moisture meager in the Plains and Midwest. Those are all negative factors for fueling severe storms that can spin up tornadoes.

Chris Dolce has been a senior meteorologist with weather.com for over 10 years after beginning his career with The Weather Channel in the early 2000s.