The temperature soared again yesterday, hitting 99 degrees, and Washingtonians did what they had to to try to keep their cool -- packing pools, buying ice by the ton and jamming museums, even the ones without rockets and prehistoric beasts.

Those who were stuck in the city stayed away from the steamy heat of the parks, but thousands flocked to the annual Hispanic Festival in Adams-Morgan, where some found that breaking into a rumba at least generated a breeze. Some who had to escape streamed toward the beaches, even though they knew full well that they were bound to be backed up in traffic at the Chesapeake Bay Bridge.

On the Delmarva Peninsula and elsewhere in Virginia, chickens died by the thousands in growers' pens. The poultry death toll for the eighth day of unrelenting heat was expected to reach 1 million in Maryland alone.

In Fairfax County, where one of the county's two water pumping stations had been knocked out of operation by a blown transformer Friday, water authority workers restored service and said water pressure was slowly rising. But 20 authority employes spent the afternoon driving around to subdivisions to ask homeowners to turn off their lawn sprinklers.

Use of water and electricity was expected to remain high for the next several days as a Bermuda high-induced heat wave continues to oppress the East Coast. A cool front may bring slightly more comfortable temperatures to this region by Tuesday, the National Weather Service said, but daytime temperatures in the 90s are expected again today and tomorrow, forecasters said.

As bad as that sounds, "it doesn't even come anywhere near to setting a record," one weather forecaster said yesterday. In 1980, Washington sweltered through 21 straight days of 90-degree heat, from July 26 to Aug. 14.

Yesterday was a day to move with extreme deliberation or not at all. Washington's giant pandas, who would likely be hunting bamboo 10,000 feet up in the mountains if they had a choice, snoozed in 65-degree air conditioning in their rooms at the National Zoo. The pandas' refusal to play ball outside disappointed fewer Saturday zoo visitors than usual. Only a third of the parking spaces were filled in the Rock Creek facility on what is usually zoo day at the zoo, police said.

The air-conditioned Smithsonian Institution museums downtown were having a field day. One visitors information center, normally not too crowded on a July day, was "absolutely jammed with people" yesterday, Smithsonian spokeswoman Madeleine Jacobs said. Said one veteran guard at the Air and Space Museum: "Everybody and his brother, and his sister, aunts and cousins are here today."

Even off the beaten track, at the lesser-traveled National Museum of American Art and National Portrait Gallery, guards were saying traffic was up about 50 percent above normal.

Ice was hot all over town. The Beverley Ice Co. established a five-year record in sales, moving nearly half a million pounds out of its 14th Street NW warehouse in 7 1/2 hours, some of it to cool drinks at the Hispanic Festival.

The festival requires so much cool that ice companies as far away as Savannah, Ga., were sending in supplies. As several thousand people moved past the festival booths lining 18th Street NW, those who did not already have a soda, lemonade, punch, beer or water in hand were in search of the coldest liquid they could find.

After five hours of festival duty, police Officer Rene C. Lewis was on patrol with a cup of lemonade in one hand and his eighth cup of water in the other. "If someone calls for help, I'll just drop them and run," Lewis said. He was tipping his hat more than usual yesterday, too. "People may think I'm just being polite, but these hats are hot and I'm trying to let a little air in."

By 2:30 p.m., when the mercury had hit 99 degrees, two visitors to the festival had fainted from the heat, police said.

There were some distractions for those who felt in need of stimulation. Chuck Marshall, who said he runs a reptiles-for-rent business in Maryland, walked along the streets with two of his workers. Around their necks were coiled pythons, ranging from eight to 12 feet long. For $5 Marshall allowed festival-goers to have their pictures taken with the snakes. At one point, however, the crowd that gathered settled for watching one of the snakes get a cooling splash at a water fountain. Marshall said the bath was just for fun.

"They don't notice the heat the way we do," Marshall said as he stroked 60-pound Neice, the python draped across his shoulder. "They like 90-degree heat. They can have a good time in this weather."

Other vendors were happy to turn up the heat, as they prepared barbecue dishes and other treats for sale. Magda Giles, a vendor sandwiched between a shish kebab stand and a fried plantains purveyor, said she planned to "dance the heat away," clapping her hands and breaking into a rumba to the sounds of the band a few feet away.

Derrick Jones and Aaron Phillips, boys who had sold $40 worth of sodas in four hours, stood beside two large plastic pails filled with sodas and no visible ice. "For you, I'll dig to the bottom where there is ice and water," Phillips said to a would-be customer. When the customer complained that the drinks looked hot, Phillips and Jones looked at each other and together said, "Get some ice."

Early yesterday, there were brief scattered storms in parts of Montgomery and Fairfax counties. That rain came as a delight to garden writer and broadcaster Jack Eden, who said he was "ready to get down on my hands and knees" if it did not rain a little.

Eden said there has been so little rain in the region that some farmers on the Eastern Shore have reported that their crops have gone dormant. New flowers may be discouraged from developing in coming weeks because of the dryness, he said, and he advised homeowners to water their lawns and plants in the morning only, because watering at night promotes plant disease.

Heat-related problems at a transmitter interrupted television transmissions on WETA (Channel 26) for a total of seven hours yesterday and Friday, a station official said.

The heat also threatened to create brush fires in dry grassy areas of the region. Maryland's fire marshal urged visitors to parks to keep camp fires to a minimum.

As Washingtonians headed for cooler parts of the region yesterday, a two-hour backup resulted at the eastbound Bay Bridge, with three-mile backups reported on the Eastern Shore routes to the beaches. Resorts in the mountains of Virginia, where temperatures were 15 degrees cooler than in Washington, reported an increase in visitors from the city.

But the heat outside was just too much for most people around here. At Seneca Creek State Park near Gaithersburg, naturalist Kerry Fitzpatrick, who had hoped for upwards of 30 participants in his morning lakeside Fishing Basics seminar, was still sounding disappointed late yesterday afternoon.

"It was a real bummer," he said. "Only three people showed up." Special correspondent Blaine P. Friedlander contributed to this report.