April Begins What's Typically The Busiest Three Months For Tornadoes In US

A​pril kicks off what's typically the busiest three months for tornadoes in the United States, but the start of this year is a reminder that destructive twisters are a danger in any month.

(MORE: Tornado Risk By Month)

W​eather History Illustrates Spring's Tornado Peak

The U.S. averaged 1,240 tornadoes annually from 2002 to 2021. About 53% of those tornadoes occurred in the months of April, May and June.

The most tornadoes typically happen in May, with an average of 277. This is followed by June and April, which average 197 and 187 tornadoes per year, respectively.

Of course, these are averages and the actual outcome can vary for how tornadic these months are in a given year. The past two Aprils demonstrate this, with 218 striking the U.S. last year compared to just 78 in 2021.

A Migration From The South To The Plains, Midwest

The areas with the biggest threat of tornadic thunderstorms slowly change as we press through the springtime months.

Much like March, parts of the Deep South still have a heightened threat of tornadoes in April. The greater potential for tornadoes then moves toward the Plains and Midwest from May to June. You can see this general month-by-month progression in the maps below.

Why The T​hreat Area Shifts Northward Later In Spring

Outbreaks of tornadoes occur when a storm system propelled by a strong, southward dip in the jet stream punches into the Plains, Midwest or South. The jet stream provides deep wind shear, or changing wind speed and direction with height, that can help form tornadic thunderstorms when Gulf of Mexico moisture is sufficient.

In spring, the jet stream begins to make its annual northward retreat toward the Canadian border.

F​arther north, it's the opposite effect since the overlap between the jet stream and increasing moisture in the atmosphere happens more often there later in spring.

Tornado Intensity Is Also A Factor

The sheer number of tornadoes from April through June isn't the only thing that makes this such a dangerous time of year – tornado intensity is also a factor.

About 58% of all twisters rated F3/EF3 or stronger (1950-2012) touched down in those three months, according to statistics compiled by Dr. Greg Forbes, formerly the severe weather expert for The Weather Channel. This rises to 69% when examining tornadoes F4/EF4 or stronger.

The most violent F5/EF5 rating has been assigned to 59 tornadoes dating back to 1950, and all but 10 of those occurred in April, May or June.

All tornadoes pose a threat, but intense twisters account for a higher number of fatalities and damage. About 86% of the deaths from 2008 through 2019 were from tornadoes rated EF3 or stronger, according to NOAA's Storm Prediction Center.

A Deadly First Three Months

This year's tornado death toll is already more than half the 49 fatalities the U.S. has averaged annually for the 10 years spanning 2012-2021. It's also surpassed last year's tornado death toll of 23.

J​an. 12 had eight tornado deaths following an outbreak that hit Alabama and Georgia. Another person died in a Feb. 26 Oklahoma twister.

M​ost recently, tornadoes in Mississippi and Alabama killed more than 20 people late March 24 into early March 25. That includes a powerful EF4 twister that devastated Rolling Fork and Silver City, Mississippi.

Now is a good time to review your plan for severe weather this spring and any other times of the year tornadoes might threaten your area.

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