The National Weather Service said Thursday that "life-threatening, catastrophic, and potentially historic" flash flooding could hit the Midwest and South with 10 to 15 inches of rainfall.
Tornadoes and large hail are also expected to batter the Ozarks, Arkansas, Louisiana, and Texas, with forecasters warning the affected communities to "prepare for possible long duration and severe disruption and severe disruptions to daily life."
It comes as the severe weather continues to cause destruction and devastation across a large part of the country, killing at least six people and injuring 13.
On Thursday, 33 million Americans from central Texas to southern Pennsylvania were at risk of strong tornadoes and large hail, and 38 million were under flood watches from northeastern Texas to northern Ohio.
