An overlooked benefit of a cold March

Tornadoes can occur year around, but the U.S. tornado season usually first gathers strength in January and February across southeastern states (Louisiana, Mississippi, Alabama, Georgia and Florida.) Then, as spring arrives and milder temperatures overtake the Great Plains and Midwest, the peak of tornado activity shifts to those regions. Coincident with the arrival of milder and more humid air, March through June constitutes the Illinois tornado season. The nation’s worst tornado disaster, the Great Tri-State Tornado of March 18, 1925, killed 695 people as it rampaged from Missouri across southern Illinois into southwest Indiana. Intense thunderstorms produce tornadoes, but thunderstorms draw their energy from mild, moist air, without which they rarely become severe. And that’s the hidden benefit of a cold March: No severe thunderstorms and no tornadoes. --By Richard Koeneman, WGN Weather Center Meteorologist