Peak activity doesn't stay in one place. Follow the jet stream and the dryline through the year and you'll see how tornado risk moves across the country month by month.
The quietest month, but not zero. Cool-season tornadoes hit the Deep South when a strong cold front collides with warm, moist Gulf air. Nocturnal outbreaks are especially dangerous.
Most affected: Mississippi, Alabama, Louisiana, Florida.
Cool-season outbreaks intensify. February 2008 had 232 tornadoes — one of the busiest cool-season months on record. The Southeast dominates.
Most affected: Mississippi, Alabama, Georgia, Tennessee.
Peak Dixie Alley season. The jet stream is still south, but Gulf moisture and CAPE are climbing. Long-track violent tornadoes are common. The March 21 1932 Deep South outbreak and 2023 Rolling Fork EF4 are examples.
Most affected: Mississippi, Alabama, Arkansas, Tennessee, Missouri.
The infamous month. Peak Dixie Alley activity crosses over with the start of Plains season. The 1974 Super Outbreak (April 3-4) and 2011 Super Outbreak (April 25-28) both fell in April.
Most affected: Alabama, Mississippi, Arkansas, Georgia, Oklahoma, Texas.
The peak. This is the month of the classic Plains supercell. The dryline is razor-sharp, dewpoints hit the 70s, shear is still strong, and the sun is high. Chase season is at maximum. Moore 1999, Moore 2013, El Reno 2013, Joplin 2011 — all May.
Most affected: Oklahoma, Kansas, Texas, Nebraska, Iowa, Missouri.
Peak season shifts north. The dryline retreats and mid-latitude storms weaken, but northern Plains storms take over. Nebraska, South Dakota, Minnesota and Iowa see their peak activity in June.
Most affected: Iowa, Minnesota, Nebraska, South Dakota, Illinois, Indiana.
Ridge builds over the central US, suppressing severe weather. Storms happen but they're often garden-variety popcorn convection. Some outbreaks tied to slow-moving upper lows.
Most affected: Upper Midwest, Northeast, Colorado.
Quiet, but capable of surprises. Landspouts spin up along old outflow boundaries. Hurricane remnants can spawn brief tornadoes across the Southeast.
Most affected: Northern Plains, Gulf Coast (from hurricanes).
Peak Atlantic hurricane season = tornado outbreaks along the East Coast from landfalling storms. Andrew (1992), Ivan (2004), Katrina (2005), Ida (2021) all spawned tornado outbreaks in landfall wakes.
Most affected: Florida, Georgia, Carolinas, Louisiana.
Fall transition. Cold fronts start advancing again but Gulf moisture retreats. Occasional strong late-season outbreaks. October 1996 saw a nasty Kansas outbreak.
Most affected: Southern Plains, Mississippi Valley.
The 'second season' peaks. Dixie Alley reactivates as cold fronts drag warm Gulf air. November 2005 (deadliest Nov outbreak) had 44 tornadoes and 33 deaths. Fall Dixie Alley is often overnight and deadly.
Most affected: Alabama, Mississippi, Tennessee, Arkansas.
Cool-season outbreaks continue. December 2021 produced the Mayfield, KY EF4 outbreak — 89 dead. Any Dec cold front reaching the Gulf can spawn violent overnight tornadoes.
Most affected: Kentucky, Tennessee, Mississippi, Alabama, Arkansas.