The Nationals ground crew holds down the tarp as severe weather approaches the stadium Tuesday evening. (John McDonnell/The Washington Post)

One child was killed and at least six others were injured Tuesday evening when a severe wind-and-rain storm swept across the Washington region, toppling trees and knocking out power to thousands.

The fatality occurred at River Valley Ranch, a camp in Carroll County, Md., which is northwest of Baltimore. As the storm loomed in the western skies, a group of children was fleeing to the shelter of a building when a tree fell on them, said Cpl. Jon Light, a spokesman for the county sheriff’s office.

He said seven were taken to hospitals, where one died. All those in the group were in the 7- to 12-year-old range, but he could give no other details about the child who was killed. Injuries to the others did not appear life-threatening, he said.

Punishing wind gusts and periods of pouring rain spread rapidly over a broad section of the region, advancing from west to east at the close of a day of steamy summertime heat.

In much of the region, the storm’s arrival, filling the skies with dark clouds, sent temperatures plunging by about 20 degrees in an hour, from sultry summer to windblown spring.

Amy Gold leads a tour group near the White House under a rainbow after a fast-moving thunderstorm passed through the Washington area on Tuesday. (Jahi Chikwendiu/The Washington Post)

In Montgomery County, one area where the storm appeared particularly severe, several large trees toppled onto streets and houses. No immediate reports of injury were received, but structural damage occurred in spots.

Trees fell onto houses in White Oak, on Huntwood Drive, and at several locations in the Potomac area, including Seven Locks Road and the 9100 block of Falls Road, according to county fire and rescue spokesman Pete Piringer.

Nearly 90,000 homes and businesses in the region were without power at times, with Montgomery and Northern Virginia seemingly most affected. Restoration efforts cut the numbers sharply, particularly in Northern Virginia, but thousands remained without electricity late last night.

Pepco issued a statement saying that it would work overnight to resolve the outages. It said the storm had knocked out one substation and 17 feeder lines. The substation had already been returned to service, the utility said.

Winds gusted with tree-toppling force in many places. One gust at the Martin Airport in Baltimore County was clocked at 61 mph. Closer to the District, a 48 mph gust was reported at Dulles International Airport, and a gust of 38 mph was clocked at Reagan National Airport.

Thousands of workers, particularly those who stayed as late as 7 p.m. or so, emerged from office buildings across the region onto wet and wind-swept streets.

The Washington Nationals baseball game, scheduled to start just after 7 p.m., was called off about 9:30 p.m.

Fans who went to see the Nationals play the Baltimore Orioles took cover in Nationals Park’s concourses, where some sat on the floor, backs against the walls, waiting expectantly, given hope by sporadic signs that the setting sun was breaking through the cloud blanket.

But it rained and rained. At National, almost three quarters of an inch fell in about three hours.

During the afternoon, Washington’s temperature had soared as high as 96 degrees. It remained only two degrees below that at 6 p.m.

Then the wind picked up, the western sky darkened ominously and the rains came. The mercury at Reagan National plunged from 94 degrees at 7 p.m. to 72 degrees at 8 p.m. Similar drops were recorded throughout the area as the storm rolled eastward from the Shenandoah Valley, triggering a flurry of storm warnings.

Although it extended a considerable distance from north to south, the line of storms was relatively narrow. As a result, while the weather enveloped the District and places to the east, the disturbance was subsiding in the region’s western reaches.

In many parts of the area, the transition from the fury of the storm to the serenity of late evening was signified by the appearance of rainbows, and even double rainbows.

The camp where the fatality occurred began operations more than 60 years ago at a site in the Millers area of Carroll County, a few miles from the border with Pennsylvania. The facility, according to its Web site, serves more than 20,000 youths and adults annually.

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