The Washington area broke century-old temperature records for a second day yesterday, as a late-spring heat wave baked residents, left power companies straining to meet demand and turned many classrooms into saunas for students not yet free for the summer.

The heat blew car radiators, softened macadam and sent people searching for refuge from 98-degree temperatures that, as they did on Monday, broke a record set in 1899, when William McKinley was president.

Today could be a bit cooler, but not by much.

"We're only talking lower 90s for a high," said AccuWeather meteorologist Mark Tobin. "The humidity might come down ever so slightly, but it's going to be quite a toasty day."

Yesterday, Potomac Electric Power Co., Virginia Power, and Baltimore Gas and Electric Co. saw power demand soar toward capacity. For the second day in a row, BGE instituted its voluntary conservation plan called "energy manager," in which a radio signal is sent to air conditioners to automatically turn off their compressors for brief periods to conserve energy.

Many schools let out early, but others didn't, consigning students -- and highly irritated teachers -- to long hours in un-air-conditioned or poorly air-conditioned classrooms.

A group of perspiring third-graders in Maryland got a vivid lesson in converting Fahrenheit to Celsius when their classroom thermometer hit 100. A Virginia principal, calling her school "Dante's Inferno," dismissed her students at 11:30 a.m.

The temperature record at Reagan National Airport was broken at 2:42 p.m., besting the previous high of 96 degrees. The record high for the date at Dulles International Airport also was broken, when the mercury hit 95 at 1:50 p.m. The old record of 93 was set in 1987. The record at Baltimore-Washington International Airport fell, too, with a 97-degree reading at 3:53 p.m., beating a mark of 95 set in 1984.

It was hot throughout the East yesterday, even in Maine, where it hit 95 in Portland. It was 96 in Harrisburg, Pa., and 99 at Newark International Airport.

Tobin said the hot, dry weather is being caused by a giant high-pressure system parked over the mid-Atlantic region, as well as the departure for Canada of the jet stream, which can funnel cool air eastward. As for precipitation, there is none in sight, he said. The nearest chance of rain is late in the weekend or early next week.

The hot day was perhaps most capricious for the area's schoolchildren. In the District and parts of Virginia, school was dismissed early. D.C. schools will close at 12:30 p.m. today as well, a schools spokeswoman said last night. But in other districts such as Montgomery County -- where most, but not all, schools are air-conditioned -- it was business as usual yesterday.

That did not go over well at Rockville's Mill Creek Towne Elementary School. The 33-year-old school lacks central air conditioning, and yesterday students were shuttled among the few classrooms and offices that had window air conditioners.

The mood was decidedly unhappy. Classes were held in first-floor corridors, where children with sweat-dampened hair fanned themselves vigorously with their hands. Others migrated through the school in search of cool and then huddled around what window units they could find.

"We're making it," said Principal Lester H. Birchall, although 60 parents came to the school and took their children home.

Outside the main office, third-grade teacher Rhoda Kupersmith was in search of a haven for her children. She had abandoned Room 23 when the Celsius thermometer on the wall hit 37, which her students knew was 100 on the Fahrenheit scale.

"We are dying," Kupersmith said, "physically, literally dying. And some of us are going to be in the hospital tonight. . . . This heat is unbelievable, unbearable. . . . This is the worst thing that's ever happened in Montgomery County."

She added, "The children should have left early. . . . We have been trying to take them to bathrooms, giving them drinks, moving them all over the building."

District students were more fortunate.

School Superintendent Arlene Ackerman said she wanted to keep schools open yesterday, but changed her mind shortly after 7 a.m. because the temperature was already soaring and officials had declared a "Code Red" air-quality alert.

She decided to dismiss at 12:30 p.m., so that children who rely on the free- and reduced-price breakfast and lunch programs would be able to eat both meals.

But there was misery in some spots in Virginia.

At Robert Frost Middle School in Fairfax County, the intense heat and a broken air-conditioner compressor combined to create what Principal Leslie Kent called "Dante's Inferno."

About half the facility was without air conditioning, and classroom temperatures soared into the mid-90s. Students were moved to the air-conditioned cafeteria and library, and some classes reassembled outside in hopes of catching a slight breeze.

"I was watching the kids get on the bus," Kent said. "They were worn down. So was the staff."

There were also problems with water.

Water pressure declined to little more than a drip in parts of Northeast Washington, near the Anacostia River.

Herman Greene, 82, who lives in 4200 block of Marne Place NE, said his water service had been sporadic since Sunday, and the flow dropped even more as the heat climbed.

"I could not take a shower; I could not wash dishes. You turn on the faucet, it is just drip, drip, drip," Greene said. "Why are people not on top of this?"

All water flow stopped at one house on Jay Street, about 10 blocks away, for several hours on Monday. It remained low yesterday. "It is the hottest day of the year and at 1 o'clock in the afternoon, the water just goes off with no warning," said Angella Barnes, 44, who has been staying with her mother in the 5100 block of Jay Street NE this week.

Libby Lawson, a spokeswoman for the D.C. Water and Sewer Authority, said the problem in that area, north of Benning Road, had been caused by a closed valve and had been corrected by late last night.

Lawson said two other sections had reported low pressure and, in some instances, no water service at all. She said the area around Bowen Road and Texas Avenue SE was affected by a break in a 12-inch-diameter water main. And repairs had affected service in the area around the 1200 block of Valley Avenue SE, including Barnaby Terrace. She said those problems also had been corrected by late last night.

Yesterday, the Loudoun County Sanitation Authority imposed voluntary restrictions on water use for its 30,000 customers. That means no lawn watering, car washing or filling of swimming pools, said general manager Dale Hammes.

Staff writers Eric Lipton, Brigid Schulte, Eric L. Wee, Martin Weil and Debbi Wilgoren contributed to this report.

Keeping Cool in the District

The District government opened five cooling centers yesterday, which will remain open until the heat wave abates. Below is a listing of these and other cooling places to which residents can go.

Cooling Centers

One Judiciary Square

441 4th Street, NW

Frank D. Reeves Center

2000 14th Street, NW

King Office Building

3720 Martin Luther King Avenue, SE

Richard England Boys and Girls Club

4103 Benning Road, NE

Department of Human Services facility

25 M Street, SW

Emergency Homeless Facilities

Mt. Vernon Trailer (Women)

New York Aveune & 7th Street, NW

Martin Luther King, Jr. Trailer (Men)

2700 Martin Luther King, Jr. Avenue, SE

Emery Trailer (Men)

17250 Lincoln Road, NE

Randall Shelter (Men)

First & I Street, SW

LaCasa Trailer (Men)

1436 Irving Street, NW

Home of Ruth/Madison facility (Women)

651 10th Street, NW

Crummell Trailer (Men)

1912 Gallauder Street, NW

Outreach/Drop-in Centers

CCH/Friendship Place

4713 Wisconsin Avenue, NW

Georgetown Ministries

1041 Wisconsin Avenue, NW

Rachael's Women Center

1222 11th Street, NW

Public Housing Senior Citizens

Arthur Capper

601 L Street, SE

Capitol View

5901 East Capitol Street

Carroll Apartments

410 M Street, SE

Claridge Towers

1221 M Street, NW

Fort Lincoln

2855 Bladensburg Road, NE

Garfield

2301 11th Street, NW

Harvard Towers

1845 Harvard Street, NW

Horizon House

1150 12th Street, NW

James Apartments

1425 N Street, NW

Knox Hill

2700 Jasper Street, SE

LeDroit

234 W Street, NW

Sibley Plaza

1140 North Capitol Street, NW

Regency House

5201 Connecticut Avenue, NW

SOURCE: District of Columbia Emergency Management Agency

CAPTION: D.C. workers Lorraine Westfield, front, and Eric Sheffey spent yesterday in a pool. Unfortunately, they weren't swimming. They were painting.

CAPTION: Debra Joseph, 27, of Bowie, cools off in the falls at the Franklin D. Roosevelt Memorial. Temperatures approached 100 degrees; today could be slightly cooler.