Storms and tornadoes left a swath of destruction that included parts of Clarksville, where three people died, and near Nashville, where three others were killed.
The storm could produce flooding, storm surge and even tornadoes through northern Florida, southeastern Georgia and coastal South Carolina in the coming days.
The complex weather system barreled through a stretch from Georgia to New York, downing trees and power lines and leaving more than a million homes and businesses without power.