One soldier was killed and five were injured last night when they were struck by lightning while playing soccer at Fort Belvoir in Fairfax County as violent thunderstorms slashed through the Washington area, ending a record eight-day heat wave.

A Fort Belvoir spokesman said the soldiers were struck about 6:30 p.m. One was dead on arrival at Dewitt Army Hospital and the five surviving soldiers were hospitalized for observation.

National Weather Service officials said Fairfax, Prince William and Arlington counties were hardest hit by the storm, which packed gusts of up to 60 mph and ripped up trees, flooded roads, disrupted subway service during last night's rush hour and cut off electricity to more than 37,000 homes. Nearly 8,000 homes were still without power early today.

Two unconfirmed tornado sightings were reported, one in Fairfax County and the other in southern Prince George's County, but National Weather Service officials said inspection of damage did not indicate that tornadoes had touched down.

The storms, which developed northwest of Dulles International Airport about 4 p.m. and swept across the area to the southeast, dumped more than 2 inches of rain by early evening and caused temperatures to plummet 21 degrees in four hours, from the day's high of 94 about 3 p.m. to 73 degrees at 7 p.m. Highs in the low 80s are forecast for today.

The scorching temperatures of the last eight days shattered a 101-year-old record for the longest stretch of 90-degree weather in September.

"We're going from bikinis to blankets," said a meteorologist.

Fort Belvoir spokesman Sgt. Edward Wise said the soldiers were playing soccer on a field adjacent to U.S. Rte. 1 on the North Post that is often used by civilians.

"It hit pretty suddenly here," Wise said. "There was a lot of rain and lightning."

No other deaths or serious injuries were attributed to the afternoon storms by local authorities.

Numerous roads were closed because of flooding, but only a portion of Firth Sterling Avenue and Suitland Parkway in the District remained blocked by standing water early today. Both were expected to reopen by the morning rush hour.

Utility officials said they expected power to be restored to all customers some time today, but at 1 a.m. more than 8,000 homes were still without electricity. A Virginia Power Co. spokesman said about 4,000 of its area customers still had no power. The outages stretched from West End in Alexandria to King's Park Shopping Center in Fairfax County and south to Old Keene Mill Road.

Pepco officials said that most of its 4,000 customers still without power were in upper Northeast Washington north of Catholic Univesity and in Prince George's County, including parts of Capitol Heights, Oxon Hill, Hyattsville and College Park.

The reported tornado sighting in Fairfax was in the King's Park area of West Springfield. Police and fire officials said high winds knocked over trees, inflicting some damage on a few automobiles and houses.

"There were broken limbs all over the place," said retired meteorologist Charles Archambault, who was driving through the area and said he saw no evidence of a tornado. "It was a very strong wind, that's all I could say."

The Weather Service said an pilot also reported seeing a twister near the Prince George's-Charles County line, but there were no reports of damage there.

The storms also created havoc for many evening rush-hour motorists and subway passengers. A 60-foot oak tree fell across Glebe Road in Arlington near Chain Bridge, snarling traffic there and flooding closed the westbound lanes of Canal Road at Foxhall Road, and traffic on the George Washington Memorial Parkway was reduced to a crawl.

Trains on the Metro Red Line were delayed more than an hour about 5 p.m. while firefighters removed trees from the tracks. Passengers were diverted to buses between the Twinbrook, Rockville and Shady Grove stations.

The heat wave began Sept. 3, when daytime highs climbed into the 90s and remained there through yesterday, setting the eight-day record. The old record was set between Sept. 4 and 10 in 1884, the weather service said. Normal highs for the first two weeks of September are in the 80s.