The Washington area continued to wilt under record-breaking high temperatures yesterday and forecasters predicted the worst is yet to come as a stagnant weather system off the Atlantic Coast pushes increasingly hot, humid air into the region.

Yesterday's high of 96 degrees at National Airport was one degree shy of the record for that date set in 1881, but the soaring heat created new records at Dulles Airport (also 96) and in other cities along the East Coast. Thousands of schoolchildren were sent home early from sweltering classrooms, where temperatures in some cases approached 100 degrees.

Schools in the District, Northern Virginia and suburban Maryland are expected to close from one to two hours early again today. Some schools also have canceled outdoor activities because of the heat.

"It's very difficult to keep the children's minds on school work," said Marilyn D. Arwood, the principal at Waynewood Elementary School in Fairfax County. "The first floor was miserable," Arwood said, and the second even worse. Teachers there moved classes into the air-conditioned library.

A mercury reading of 98 in Baltimore shattered the previous high set there two years ago, and in Norfolk the temperature reached 97, breaking a record that had stood more than 100 years.

Air conditioners were cranked into high gear throughout the area. Virginia Power Co. reported record electrical use for the month of September. Many motorists were stranded as engines overheated and tires blew.

The heat wave arrived just as many people were returning to work from the Labor Day weekend and expecting the traditional miseries of summer in Washington to trail off toward fall.

"I think that's also why it feels so much hotter," said National Weather Service forecaster Scott Prosise, noting that the area usually has several 90-degree days this time of year.

"You think you've turned the corner at Labor Day and you're expecting leaves to turn color and, Boom!, you run right smack into hot weather," he said.

Most area residents apparently weren't taking any chances with the heat. Hospitals around the Beltway reported very few admissions for heat-related problems, although a few people with allergies and other respiratory ailments suffered.

"It almost appears that with the kids back in school, outdoor acitivity has been reduced," said Tony DeStefano of the Prince George's County fire department. "The older folks now generally know to stay indoors during days of high heat and humidity. And we're grateful for that because we don't need them as customers."

"When you have an unexpected heat wave in April and May, you see problems," said Teresa Fulton, spokeswoman for Children's Hospital. "But at this time of the year, people have come to expect it."

Thousands of people going back to work after vacation season, though, means more cars on the road and more pollution. The D.C. Lung Association yesterday reported an air quality reading of 90. The association issues health warnings when the index passes 100, as it did Aug. 13 when the temperature hit 94 and the air index was 125.

Even worse for people with allergies, this is the beginning of ragweed season.

"For people who have respiratory ailments, this is a really bad time," said Victor Harry, an allergist at Greater Southeast Community Hospital. "The high temperatures make ragweed season even worse. It's very easy for people to go into spasms."

But at least one person saw the heat as a chance to get outside. At the East Potomac Park golf course, business was slow yesterday and the resident golf pro, Ray Crampton, teed off on the sun-parched links.

"When you're a golf pro, you only get a few times out and this is it," Crampton said.

According to weather forecaster Prosise, the source of Washington's weather woes is a high pressure system stationed off the coast of South Carolina. Such systems are typical at this time of year, he said, but in this case there is virtually no air movement in the upper atmosphere to push it away.

The weather will become increasingly muggy as the humidity level rises over the weekend, Prosise said, but there may be relief by Tuesday when a cool front moves in from Canada, possibly bringing showers as well.

"Until then," he said, "we're just going to have to sweat it out."