Why April, May And June Are The Most Active Months For Tornadoes, Especially For Intense to Violent Twisters

Yahoo

24-03-2025

Tornadoes can strike certain parts of the U.S. at any time of year, but April, May and June are overwhelmingly the most active when it comes to thunderstorms spawning these destructive forces of nature.
Here's a look at several of the trends that show why these springtime and early summer months are such a dangerous time of year for tornadoes.
Spring's tornado threat area grows in size… and shifts: The areas with the biggest threat of tornadic thunderstorms slowly change as we press through the springtime months.
Similar to March, much of the Deep South has 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.
(MORE: Tornado Risk By Month)
The peak in spring's tornado activity is illustrated by recent weather history: The U.S. averaged 1,246 tornadoes annually from 2004 to 2023. About 52% of those tornadoes occurred in April, May and June.
The most tornadoes typically happen in May, with an average of 260. This is followed by April and June, which average 202 and 186 tornadoes per year, respectively.
Of course, these are averages. How tornadic these months are in a given year can vary, often dependent on when major tornado outbreaks occur. Some recent Aprils demonstrate this, with 356 tornadoes striking the U.S. in April of 2024 but only 78 in 2021.
Tornado intensity is also a factor in making this a dangerous time of year: About 58% of all twisters rated F3/EF3 or stronger (1950-2012) struck in those three months, according to statistics compiled by Dr. Greg Forbes, former severe weather expert at 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.
(MORE: Where Have All The EF5 Tornadoes Gone? The Surprising Reason Behind The 11-Year Drought)
All tornadoes pose a threat, but intense twisters account for a higher number of fatalities and damage. About 83% of the deaths from 2019 through 2023 were from tornadoes rated EF3 or stronger, according to data from NOAA's Storm Prediction Center.
The ingredients that come together to spawn tornadoes align most often 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 there's enough moisture drawn northward from the Gulf.
As spring progresses, the jet stream begins to make its annual northward retreat toward the Canadian border.
That's why the potential for tornadoes in the South is much lower in June compared to April. Although moisture is abundant across the South in late spring, the strong jet stream needed to help make conditions favorable for tornadic thunderstorms is usually absent.
Farther north, it's the opposite effect: the tornado threat is greater in June than in April. The overlap between the jet stream and increasing moisture in the atmosphere happens more often there later in spring.
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.
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.