Post reader Michael Hutshneker snapped this photo of a downed tree at the 1500 block of P Street NW. (User-submitted photo)

A man on a bicycle was struck by a falling tree and killed Sunday night on the C&O Canal towpath during the day’s second round of spectacular thunderstorms, which knocked out power to thousands of homes and drenched the area with rain.

The man, who was thought to be in his early 50s, was struck about 7:50 p.m. while riding in upper Montgomery County, near White’s Ferry, said Bill Line, a spokesman for the National Park Service.

Line said that the man, who had not been identified, was pronounced dead at the scene and that it “seemed clear” that a tree fell on him, knocking him off the bike.

The evening’s storms knocked down trees throughout much of the area, including Capitol Hill in the District, the Cherrydale section of Arlington County and parts of the George Washington Memorial Parkway in Northern Virginia. Trees were reported down on the west side of the Capitol, and nearby roads were closed.

Hail was reported in Prince William County, a roof was set afire by lightning in the Bowie area of Prince George’s County, and people who lingered on the Mall after the day’s events at the Smithsonian Folklife Festival were told to seek shelter.

People are evacuated from the West Lawn of the U.S. Capitol (Keith Stefanelli /User-submitted photo)

At least one gust of wind was measured at 58 mph Sunday night in the District. Flights were held on the ground for more than an hour at Reagan National Airport.

About 9 p.m., more than 40,000 homes and businesses in Northern Virginia, the District and the Maryland suburbs were reported without electricity. About half were in the Pepco service area, and half were in the Dominion Power area.

Sgt. Kimberly Schneider, a spokeswoman for the Capitol Police, said authorities evacuated people who went to the Capitol’s west lawn for the rehearsal of the annual Capitol Fourth concert.

She said they were sent to a “safe harbor” on the Capitol grounds. It was then decided that it would not be safe for them to return to the rehearsal.

A spokeswoman for the Folklife Festival said two concerts that were to be held Sunday evening were canceled.

Both Schneider and Folklife spokeswoman Becky Haberacker said today’s July 4th programs would go on as scheduled.

“We will of course monitor the weather,” Schneider said. The National Weather Service forecast called for a 20 percent chance of isolated showers and thunderstorms in the afternoon. The forecast for the evening made no mention of rain.

If the evening’s storms seemed ferocious, the storms that erupted before dawn were spectacular, too, with peals of thunder and flashes of lightning that turned the sky white.

At the National Weather Service measuring station in the Camp Springs/Andrews Air Force Base area, the evening storms brought more than eight-tenths of an inch of rain. The morning storms brought about one-third of an inch. The total for Sunday was 1.16 inches.

At National Airport, .69 inches was measured between 3 and 8 a.m.

In the evening, skies suddenly grew black, trees tossed their branches, streetlights swayed and large, swirling drops of wind-driven rain filled the sky like a water gushing from a firehose. The official rainfall figure at National was only about one-fifth of an inch.

In between periods of storminess, Washington experienced a hot and humid July 3, with a high temperature at National of 92 degrees and a high at Dulles International Airport of 95.