How hot was it yesterday? Up to 102 degrees at Reagan National Airport, breaking an 80-year-old record for the date. So hot that a section of Columbia Pike buckled, forcing Howard County police to close part of the roadway in Columbia. So hot that the National Weather Service warned of extreme heat from the Mississippi Valley to the East Coast.

And the furnacelike temperatures are expected to persist today. As for air quality, the Metropolitan Council of Governments issued its second consecutive "code orange," warning of "moderately unhealthy" conditions.

D.C. School Superintendent Arlene Ackerman ordered the city's summer school sessions to close today, and the first official day of work for the 7,000 youths in the city's summer youth employment program, which was to start today, was postponed.

The heat yesterday came early and stayed late.

"I got to work at 8:30, and there were already 25 or 30 cars waiting to get into the parking lot," said Debbie Daniel, spokeswoman for Six Flags America in Largo. "A lot of people came and camped out at the water park all day."

The temperatures also topped out at 102 at Baltimore-Washington International Airport. Dewey Walston, a Weather Service meteorologist, said the thermometer today may well break the 100-degree mark for Washington set in 1977 before cooling down--if that's the right term--a bit tomorrow.

Utility companies did their best yesterday to keep up with the demand for air-conditioned cool.

About 4,000 Potomac Electric Power Co. customers were without electricity at 9 p.m., largely the result of blown fuses and transformers, said Makini Street, a Pepco spokeswoman.

In Ocean City, Md., thousands of residents and vacationers had a hard time keeping their cool late in the afternoon when power failed between 114th and 122nd streets, an area packed with high-rise condominium buildings. Electricity was restored within about two hours, officials said.

Virginia Power spokeswoman Barbara Gordon reported only minor outages over the holiday weekend, but she said she expects the demand to peak today around 6 p.m., when computers and other electric products are in widespread use and people click on their air conditioners when they return from work.

"We think we're okay, and we don't expect any problems. We expect to meet all the demand," Gordon said.

Pepco officials issued an "energy conservation reminder" in anticipation of continued high demand today. Pepco asked customers to consider not using heat-producing appliances such as stoves and dryers until the evening; setting the air conditioner thermostat higher than normal; turning off nonessential appliances and all lights possible; and closing curtains and blinds during daylight hours to prevent heat buildup.

In Howard County, police closed Columbia Pike between Johns Hopkins Road and Route 216 for several hours while emergency road crews smoothed out the twisted pavement, officials said.

In Northern Virginia, state troopers said, the heat disabled at least 30 vehicles. The Maryland State Police barracks in College Park said it received 20 reports in one hour alone.

In the District, dozens of people sought relief at the city's five cooling stations. The facilities will open today at 10 a.m. and close at dusk.

Six people were treated yesterday for heat-related problems at Loudoun Hospital Center in Leesburg, said Michael Carrozza, a nursing supervisor. Four elderly patients were admitted to Suburban Hospital in Bethesda showing signs of severe dehydration, a spokeswoman said, and at least two people were admitted to Howard University Hospital for heat-related stress, said Melissa Clark, a hospital spokeswoman. A 7-year-old boy was taken to Georgetown University Hospital saying he felt "dizzy and sweaty," said Nancy Whelan, a hospital spokeswoman.

But fewer people sought help at hospitals than on Sunday, when George Washington University Hospital treated 29 patients for heat-related problems. Most had spent the day on the Mall for Fourth of July festivities, a spokeswoman said.

The hospital stocked up on water and emergency supplies yesterday and had treated four patients for heat-related symptoms as of 6 p.m. "We're still getting ready for a lot of people. Anything could happen," said Amy Pianalto, the hospital's spokeswoman.

Advised a nursing supervisor at a Virginia hospital: "Don't even wash your car. Put a fan on, a cool towel on your face."

William Rogers, director of emergency services at Inova Alexandria Hospital, said that drinking plenty of water isn't enough to stave off the heat's ill effects. Eat french fries, potato chips and other foods with a lot of salt, he said.

The heat wave has been fueled by a mound of high pressure pumping hot air over the region, from West Virginia to New England.

The mercury hit 101 in Baltimore at 4:12 p.m. yesterday, breaking the 100-degree mark set in 1990.

Raleigh-Durham, N.C., topped out at 102. New York City hit a record 101, Bridgeport, Conn., registered 100 and Philadelphia tied its record at 100. In Cincinnati, a thermometer stuck in the artificial turf at Cinergy Field measured 154 degrees, while the air temperature registered 89.

A measure of relief could be on the way. Walston said a cold front is expected to move into the mid-Atlantic region tomorrow night.

"We'll just drop back off a little bit, and the humidity will come down," Walston said. "After 102- and 103-degree days, it'll be a little bit better."

In the heat of the moment, people coped the best they could.

At the Takoma Park Independence Day Parade yesterday, crowds ducked under spreading trees to avoid the hot sun, creating tight clusters of people and large sections of empty curb. Many parents brought tiny battery-powered fans to keep their children cool.

Everyone seemed to have a bottle of water, including participants in the parade. Bands and dancing groups kept refreshment handy by having volunteers drag small red wagons and drive cars behind them carrying gallon jugs of water.

Staff writers Spencer S. Hsu, Brian Mooar, Mary Louise Schumacher and Maria Glod contributed to this report.

CAPTION: Zamonte Hamlet, 5, enjoys a cool spray at his grandmother's Alexandria home. The temperature at nearby Reagan National Airport set a record at 102 degrees, and today's forecast is much the same.

CAPTION: Cameron Run Regional Park in Alexandria drew plenty of people looking for a way to wash away the heat wave.

CAPTION: Lifeguard Lori Gavaghan keeps watch over a capacity crowd cooling off at Cameron Run Regional Park in Alexandria. (Photo ran on page A01)