Severe weather threatens the South with hail, tornadoes By (0) A dangerous severe weather outbreak could put at least 17 states and more than 100 million Americans at risk across the United States this week, AccuWeather forecasters warn. Severe thunderstorms will erupt each day through Thursday across parts of the southern U.S., with the greatest threat and potential for tornadoes Wednesday, lasting well into the nighttime hours, and Thursday. Advertisement All facets of severe weather ranging from large hail and flash flooding to damaging straight-line wind gusts and tornadoes can occur from Tuesday evening through Thursday evening in what is likely to evolve into a significant severe thunderstorm and tornado outbreak.