“Widespread flash flooding has occurred this morning across the D.C. metro area,” the National Weather Service said in a statement. “Much of this flooding is subsiding and the heavy rain is over. Some of the larger streams are still rising, however, so flooding and road closures will continue through the afternoon.”

The National Weather Service advised people to turn around if they encountered flooded roads, and said most drowning deaths during a flash flood happen inside vehicles.

The Fairfax County Fire and Rescue Department said it had responded to 55 swift water rescue calls on Monday morning, including the evacuation of multiple people from a block of mobile homes. There were no reported injuries, but thousands were without power.

In Washington, floodwaters stranded motorists on the roofs of their cars in Northwest D.C. The D.C. Fire and E.M.S. Department said it had rescued 15 people across the city who had been stranded atop their cars in high waters.