National Guard deployed

Florida Governor Rick Scott, who issued a state of emergency on Saturday in all of the state's 67 counties, said on Sunday that the Florida National Guard had 5,500 guard members ready to be deployed if needed.

"If evacuations have been ordered in your community, do not ignore them," Scott said on his Twitter feed.

The National Weather Service has issued a flash flood watch for an area stretching from Mississippi to North Carolina that is home to millions of people.

Alberto's projected storm track has shifted eastward since Friday, lessening its threat to the active oil production areas in the Gulf of Mexico. Royal Dutch Shell Plc, Exxon Mobil Corp and Chevron Corp have evacuated some personnel from offshore Gulf oil facilities.

A separate storm system on Sunday caused flash flooding in the Baltimore suburb of Ellicott City, Maryland, turning its historic Main Street into a raging river with water reaching past the first floor of buildings and sweeping cars down the road, local news video showed.

Governor Larry Hogan declared a state of emergency for the area rebuilding from a devastating flood about two years ago that killed two people and damaged dozens of buildings.