The mayor of Alexandria said he was sweating off weight to raise money for charity. A Swedish tourist who found the sticky humidity foreign to him kept jumping in a hotel pool. Sweltering grown-ups sought rest, shade and air conditioning while children played, seemingly oblivious to the weather.

As temperatures in the Washington area reached the 90s for the 11th time this month, residents and visitors coped as best they could yesterday with the oppressive midsummer heat and humidity that are as much a Washington trademark as the Mall and the monuments.

Wary of the hot streets, people went to the movies or played them at home on their videocasette recorders. Picknickers enjoyed a breeze in Rock Creek Park. A bicyclist said she had become accustomed to perspiration, and some of the visitors to the Lincoln Memorial shed their shirts.

Yesterday evening, fueled by the steamy heat, spectacular thunderstorms swept across the area, unleashing high winds and vivid bolts of lightning that knocked out power to an estimated 33,000 homes.

Billowing black clouds poured pea-sized hailstones and torrents of rain on some sec- tions. About an inch and a half of rain fell in part of Montgomery County, while winds there gusted up to 50 miles an hour, the National Weather Service reported.

As trees toppled and branches snapped, electricity was cut off to about 20,000 homes in the city and the Maryland suburbs, the Potomac Electric Power Co. reported. Many of the affected homes were in Montgomery. Virginia Power said about 13,000 of its customers lost power during and after the storm.

Investigators were checking to determine whether lightning may have caused a two-alarm fire in Fairfax.

The storm sent temperatures at National Airport plunging 16 degrees in an hour. Today's high is expected to be near 90 again.

Well before the storm struck, taxi driver Ali Heider found himself on the city's sultry streets with a heat wave in progress and his cab's air conditioner on the blink.

"I have nothing to keep myself cool," he told a reporter. "I can do nothing. I am suffering."

A woman outdoors in Georgetown said it was not her idea. She said she was running errands with her husband and daughter because the family is moving into a new house.

"We wouldn't be out if we didn't have to be," said the woman, who declined to give her name. "We have no choice."

Another woman, Ellen Way, said she found it possible to do her shopping and beat the heat.

"I drove down in an air-conditioned car, had lunch at an air-conditioned restaurant and have been shopping in air-conditioned stores," she said.

Maureen Murphy, who works at the Crabtree and Evelyn store in the Georgetown Park shopping mall said the store was "somewhat busier than usual for a Sunday in July."

Tory Shirley said she and friends settled on the air-conditioned mall as a second choice. First choice was a movie. But at the theaters, "the lines have been too long," she said. "Everybody wants to be inside."

For some Washingtonians, being inside and watching a movie meant staying home with the air conditioner running and the VCR playing.

Gerald Joireman, 50, who was on his way to a Silver Spring store that rents videocassettes, said he has adopted a four-movie-a-day diet because of the heat.

"We just sit around, turn the AC down and do nothing but watch movies," he said.

He enjoys movies in theaters, also, he said, but under current conditions, "I don't even want to go out to do that."

Despite the heat, some people, with varying degrees of enthusiasm or resignation, did spend much of the day outside, employing a variety of techniques to obtain a degree of comfort.

One of them, Thomas Gaynor, 35, a resident of the Shaw area, said he had no air conditioning, making days like yesterday "really terrible."

"We have fans," he said, sipping Gatorade and mopping his forehead with a towel, "but they just move the air around. An air conditioner would be really nice right now."

Children at Sixth and P streets NW played in the spray of an open fire hydrant. Derrick Walker, 12, rubbed a Popsicle over his face, smearing the ice through his hair.

Lionel Smith, 62, sat in the shade of the awning of the Giant Food store at Eighth and P streets NW.

"I find shady spots and sit down," he said. "That's my secret."

Ruby Greenspan of Reston was riding her bicycle around Washington. "You just get used to being sweaty all the time." she said. "Life doesn't stop every time the weather changes."

Although it was unarguably hot, "it's not too hot to be in the park," said Velma Greenfield, one of about 100 persons at a family reunion and picnic held yesterday near Pierce Mill in Rock Creek Park.

"It's pretty cool with a breeze blowing through the trees. The old people just have to move a little slower," she said. "But just look at those kids," she said, noting the vigorous activity of family youngsters. "The heat doesn't bother them at all."

As if to underscore her words, Bernard Maurice Frazier, 4, acknowledged that he was hot, but insisted "I don't care."

As perspiration dripped from his face, he said, "I just want to play baseball."

Although still in nursery school, he said he already knew a method of summer survival: "When it gets hot and I get thirsty, I can drink water."

On the roof of the Thomas Circle Holiday Inn, John Lindhe, a businessman from overseas, having discovered the discomforts of Washington in summer, sat by the pool.

"I am from Scandinavia and we do not have this, this damp there, you know?" he said. "It's so damp." To avoid the effects of the humidity, he jumped in the water at 10-minute intervals.

At the Lincoln Memorial, park ranger John Conlan said visitors were "moving a lot slower" but were "still here" in "basic summer Washington wear -- shorts, T-shirt, no shirt . . . very lightly dressed."

At home in Alexandria, Mayor James P. Moran Jr. was sweating out the heat wave, which, he said, was helping him sweat off pounds as a means of raising money for charity.

For each pound he loses before Sept. 9, he said, donors have pledged to contribute to a shelter for runaway youth. "The hot weather is a blessing," he said.

D.C. Council member John Ray (D-At Large) went to a meeting. His wife Sarah and their three children tried to stay cool in their small backyard wading pool. Hilda Pemberton, vice chairman of the Prince George's County Council, stayed home, "taking it easy, doing some mundane house work and preparing dinner and getting ready" to go to an evening political meeting.

The air conditioning was on. "Very much so," she said.

Mary Margaret Whipple, chairman of the Arlington County Board, found another way to avoid the heat. She was on vacation, her daughter, Margie, said. In Canada.

Staff writers Alexandra Clough, Jeffrey Goldberg, Lisa Leff, Douglas Stevenson and Valca Valentine contributed to this report.