A mass of hot and heavy air known as a Bermuda high pressure system continued to oppress the Washington area yesterday, wilting those brave enough to spend time outdoors.

Although yesterday's high temperature of 96 degrees did not break the record for the day--103, set in 1887--the heat was more than enough to jam area swimming pools, fray motorists' tempers and set off a scramble to buy electric fans.

"We had four different fans on sale today, and they bought them all," said Leander McDonald, assistant manager at the area's largest Hechinger's hardware store. The entire stock of more than 100 fans was gone just 90 minutes after they opened the doors. "We don't even have any displays left," McDonald added.

Over 1,000 people flocked to the pool at Lake Fairfax Park in Reston, scores more than normal for a weekend day, a spokesman said. And the Pohick public pool in Fairfax reported that 1,800 people--a summer record--had stopped by for a dip by early evening.

"They're all bumping into each other," said the pool manager, who had eight lifeguards on duty.

People sought relief any way they could. The telephones at Custom Air Conditioning and Refrigeration Service of Fairfax City were ringing off the hook and a spokesman said the firm was five hours behind in its service calls.

The Bermuda high, a system of sticky summer air stretching from Maine to the Carolinas, rolled into the area 10 days ago, "and we haven't had a change of air mass since," said David Caldwell of the National Weather Service.

The high caused record heat in Boston with 98 degrees and discomfort from Maine to Florida. Fat and lazy astride the east coast, the air mass has blocked cooler winds from the north at the Pennsylvania border. One such front of cooler air is expected to approach from the Great Lakes tomorrow, "but because the high is sitting over us and not inclined to move, the front will not push south," Caldwell said.

The thermometer may dip into the upper 80's by mid-week, but can be expected to reach the 90's by the weekend if the Bermuda high remains strong, Caldwell said.

The high has trapped area pollution under its high pressure dome, causing the weather service to issue a stagnant air advisory for central Maryland for the third straight day. People with heart and respiratory problems are urged to remain indoors, preferably with air-conditioning.

However, several older health facilities throughout the area lack air-conditioning. In those institutions, it was a particularly uncomfortable day.

At the Maryland state psychiatric hospital in Crownsville, patients sat in day rooms yesterday, hoping to catch the breeze from wall mounted electric fans, according to a nurse on duty at the 71-year-old facility.

"It's unfortunate," she said. "People suffer when they're hospitalized, when they're not allowed to leave and cannot change their environment."

Most of the students at Prince George's Cheltenham Center for the emotionally disturbed were home for the weekend, but for a half dozen resident students and about 20 staffers, "it is miserable," said resident counselor Aubrey Baker.

"We have only one air-conditioner and it's in the front office. We can't fit all the kids in there," Baker said. "We've got all the windows up sky high, but it's still hot."

Meanwhile, 30 workers at Pepco's Potomac generating plant were working in temperatures between 112 and 120 degrees just to keep power customers cool. Power consumption was up for the weekend, according to Pepco spokeswoman Nancy Moses, but not at a record level.

"It's a good heavy load," Moses said. A record peak of 4,152 megawatts was consumed last July 9 when the temperature reached 98 degrees, still well below the capacity of 5,349 megawatts, Moses said.

Despite the heat, area fire and rescue squads did not report any unusual increases in heat-related ambulance runs. Holy Cross Hospital of Silver Spring reported one youth was treated for dehydration after he passed out while playing baseball. A handful of heat-related cases were treated at Suburban Hospital in Bethesda.

"I think people are getting smart," said a Prince George's firefighter. "They're not going out there today."