Washington staggered through one of the hottest, muggiest 24-hour periods in the 110 years that records have been kept as temperatures yesterday morning bottomed at 82 degrees and then peaked at 98 during the day.

Yesterday's high, recorded at 3:05 p.m. at National Airport, was almost 10 dgrees above normal for this time of year. The resulting demand for electricity to power air conditioners reached a season high, rivaling the power drain normally experienced in late July and August when Washington's weather is at its worst, power company officials said.

The National Weather Service held out hope that relief might be on the way today as the large mass of near-stagnant air that has enveloped the East Coast for several days slides out over the Atlantic. While temperatures are expected to remain in the 90s, the air mass should take much of the energy-sapping humidity with it.

The loses midnight-to-midnight temperature yesterday -- 82 -- was recorded at 5:40 a.m. It erased the old mark of 81 degrees, which has occurred here six times, most recently last July 20. To complicate further the routine of living through such a day, the humidity reached 75 at 7 a.m., just when the thermometer was in the early stages of its drive to 98 degrees.

The Air Quality Index that measures pollution soared to an unhealthful reading of 105 on Wednesday but fell to 65 yesterday as the air mass began to move, nudged along by a cool front moving slowly across the midwest.

All over the Washington Area people scrambled for ways to beat the heat.

A spokesman for Metro said the subway system, where temperatures can be 60 degrees in its underground stations, registered an increase in riders. "It's the coolest place in town, a few more bucks for the fare gate. It's the biggest baby sitter for mothers in the land," the spokesman said.

At Union Station, about a dozen boys and girls splashed in the fountain yesterday, a less-croweded alternative to costly private pools and popular public pools in the area. "It's never really crowded here," said 12-year-old Michael Joyner as he frolicked with friends.

The Olympic-sized pool in East Potomac Park, on the other hand, was jammed according to manager Henry Agusiewicz.

"You don't see many on the deck, most are in the water," said Agusiewicz, who first worked at the pool as a lifeguard in 1939 and has managed it for the last 30 years. Officially, he said, the pool holds 400 swimmers, but "I don't want to tell you how many I have. My gosh, you couldn't possible hold them out."

While many sought out cool public places, apparently many others thought it was better to just stay home and move around as little as possible.

At Greenleaf Gardens, a high-rise public housing profect in Southwest, there were few takers for a free-hour of roller skating sponsored by the D.C. Recreation Department and local Girl Scouts.

"We can't get anybody out. Free skating . . . and they're passing it up," said Gwendolyn Henderson, a Girl Scout program coordinator.

Even the Smithsonian Institution, with its cool museums, reported that crowds in its buildings were smaller than usual while Washington's ubiquitous joggers seemed to be out in fewer numbers.

Some area hospitals were issuing instructions on how to stay cool but there were only scattered reports of heat-related illnesses.

At Washington Hospital Center, student nurses trying to beat the heat by taking a plunge in the school pool found it already occupied by a Mallard duck and five ducklings.

Spokeswoman Jane Snyder said the duck family was moved from the pool to a nearby reservoir a couple of weeks ago but had managed to find its way back. "It's the second year for the duck. She lays her eggs near the pool," Snyder said.

The ducks' presence did not deter the nurses, who promptly joined them in the pool, Snyder said.

Had the hot spell occurred before July 1, many federal employes might have gone home early yesterday, but last week a new federal regulation went into effect that greatly reduces the leeway of federal office managers to allow their office workers to leave work and still collect pay because of uncomfortable working conditions.

Now employes who think they are too hot to work must take their own annual leave if they want off. Only if entire office or building cooling systems break down can managers close down for the day.

Cody Pfanstiehl, spokesman for Metro, said 172 of its 1,500 buses were out of service because air conditioners were not working. He said the system was having it usual summertime problems with overheated buses and passengers who insist on opening windows to "stick their elbows out and expect the air conditioning to work."

At the National Weather Service in Camp Springs, forecaster Dorothy kropp said the temperature was starting to get to the computers that transmit weather data. "The air conditioner is working just enough to keep us from passing out," she said.

The all-time high for July 9 was set in 1936 when the temperature hit 104 degrees, with the record low of 55 in 1891. The normal high and low are 88 and 69, the weather service said.

"It should be fairly pleasant, drier and more normal" today, Kropp said. "I'm looking forward to it."

That was little consolation to people yesterday, who, like postal service carrier Roderick Hicks, sweated and strained in the heat.

Hicks said it was pretty rough being out, "especially when you're carrying 50 pounds and all I hear is, 'My, how hot it is today,' from people in air-conditioned buildings."