While severe weather can happen at any time, tornadoes tend to strike the state more during spring and fall. In these months, warm air mixed with cold fronts makes for a perfect storm that can lead to twisters.
Tornadoes are becoming more common in the southern United States, and they are increasing in places east of Tornado Alley, according to a study by Northern Illinois University meteorology professor Victor Gensini and University of Alabama assistant professor of atmospheric sciences Matthew Brooks. Specifically, the Gulf of Mexico's warming caused by climate change is allowing more moisture to reach Tornado Alley, which in turn creates more tornadoes, they say.
A combination of a natural La Nina weather cycle and Gulf of Mexico temperatures that are above average this time of year caused an outbreak of tornadoes in the region Thursday, experts said. Those conditions combined with decades-long trends toward more tornadoes moving eastward have created a deadly mix of factors, Gensini told PEOPLE.
The outbreak hit the Southeast, including Alabama and Georgia, on Thursday afternoon, killing at least seven people, sending thousands without power and leaving a trail of debris across the region. In Autauga County, a massive tornado swept through the town of Selma, wrecking buildings, snatching vehicles and ripping away trees in the historic city's downtown area.
Search teams were on the ground looking for victims in the storm, and several counties have issued tornado warnings. The National Weather Service reported more than a dozen tornadoes in the southern half of Alabama, along with several reports of significant damage and injuries in Georgia.