As one sodden Friday hour succeeded another, the total rainfall measured since May 12 reached five inches and kept climbing.
No matter how firmly tree roots might be lodged, that much water may loosen their grip.
In one of the more serious incidents, a motorist was injured in Montgomery County, Md., on Friday afternoon when a tree crashed through the windshield of a moving SUV on Interstate 270 just north of the Capital Beltway, authorities said.
“You don’t expect to be hit by a tree on I-270” said Pete Piringer, spokesman for the county fire and rescue service.
An injury was also reported in Arlington, Va., when a tree toppled onto a house in the 2100 block of North Vernon Street, officials said.
And on Seminary Road in Alexandria, Va., a motorist had just read a warning about tree hazards when one came down, prompting this Twitter message: “Literally just fell in front of me. “
This story has been updated.