Widespread thunderstorms were rolling across the central US and heading east on Tuesday bringing tennis ball-sized hail, pounding rain, dangerous winds and possible tornadoes to at least 75 million people.
More than three millions residents in Tennessee were under a tornado watch on Tuesday afternoon, in the Nashville area, with potential for twisters from southeast Virginia to northeast South Carolina.
More than 200,000 residents had lost power across West Virginia, Ohio, Indiana and Kentucky.
Damage to houses, trees and power lines has been reported from Texas to Kentucky with dust storms causing cars to pile up on highways. At least one person was injured in Lexington after severe early morning storms on Tuesday.
Residents shared videos of cracked windshields and hail the size of a person's palm.
The powerful storms could extend into Wednesday, forecasters say.
After lashing parts of Texas, Illinois and Oklahoma, the weather system moved from the northern parts of Indiana and Ohio and western Pennsylvania on its track east.
The risk for tornadoes extends from southeast Indiana across Ohio and over portions of Kentucky, West Virginia and Pennsylvania, the Storm Prediction Centre said.