In the relatively confined zones deluged late Saturday and early Sunday, intense rain quickly overwhelmed Rock Creek in the District and Sligo Creek in Maryland. Rescuers aided occupants of stalled cars near both, authorities said.
Within a couple of hours, the water surging down Rock Creek at Joyce Road was 100 times greater, according to U.S. Geological Survey data.
While turbulent drama played out in some places overnight, much of Northern Virginia and downtown D.C. saw little or nothing.
But even in downtown, where a few clouds floated in a blue afternoon sky, signs could be seen. Beneath the Pennsylvania Avenue Bridge between Georgetown and Foggy Bottom, Rock Creek rushed toward the Potomac River, brown with silty runoff, and foaming over and around rocks in the creekbed.