From Houston and New Orleans, up to Indianapolis and Cincinnati, 50 million Americans are at risk for severe weather today, including flash flooding, damaging winds, tornadoes and large hail.
The rain is already underway, with flash flood watches in effect from Indianapolis to Pittsburgh.
Memphis, Nashville, Evansville, Louisville, Cincinnati and Indianapolis are most at risk for winds and tornadoes from this afternoon until about midnight.
Tornado watches are extending across Arkansas, Tennessee, Missouri, Illinois, Kentucky, Indiana and Ohio through 8 p.m. Winds may reach up to 70 mph.
Meanwhile, Minneapolis to Green Bay to northern Michigan are under winter storm warnings as some areas could see up to 1 foot of snow.
By Wednesday, the snow will be done, and on Thursday, a cold blast will head to the Midwest and East Coast.
The Thursday morning wind chills may reach 3 degrees in Green Bay, 20 degrees in Chicago and 26 degrees in New York.
Even the South will feel the cold. Wind chills may reach 35 degrees in Memphis, 36 in Atlanta and 38 in Raleigh.