Utility companies across the mid-Atlantic region strained to prevent a broad power failure yesterday as consumption reached record highs amid suffocating heat that killed at least two District residents.

Temperatures reached a record high of 103 degrees for the date in Washington as Pepco and utilities in Pennsylvania and New Jersey reduced voltage by 5 percent to meet the escalating demand for power. Utility officials compared the move to reducing water pressure and warned that if consumption did not decline, they would impose temporary planned blackouts to "prevent the complete failure of the electric power grid" that serves 22 million customers.

"Everything is running flat out," said Doug Burnes, the control center operator at Potomac Electric Power Co.'s generating plant in Alexandria.

Yesterday was the third straight day in which temperatures exceeded 98 degrees across the Washington area. Nationally, the heat has been blamed for at least eight deaths in the Midwest and East. It also stalled commuter trains and subways in New York and forced summer schools across the country to cancel classes or send children home early.

In the District, a 73-year-old woman perished in her humid Northeast Washington home. Mary Northington was pronounced dead at Howard University Hospital of cardiac arrest with a body temperature of 105 degrees -- more than 6 degrees above normal. A second death also was attributed to the heat, but Howard University Hospital officials declined to release the name of the victim.

In Montgomery County, emergency crews evacuated a high-rise senior housing complex after its air conditioning failed the previous day. As temperatures rose, emergency workers forced scores of residents of Leafy House in Kensington to leave stifling apartments, although some were reluctant to go.

The result was a tableau of sweat and discomfort, as dozens of perspiring elderly residents, some in wheelchairs and with walkers, waited with belongings for relatives to pick them up. Those who have no local family were transported on county Ride-On buses to five other county-run complexes where the air conditioning was working.

Sue Singer, 74, said she survived the previous evening "by the grace of God" and by applying ice-filled washcloths to her face and neck.

"We can't predict what Mother Nature has in store for us," she said. "It's been a little bad, but you know how she handles things."

Nearby, John McNickle, 70, was picking up his sister, Mary McNickle, and loading her oxygen machine into the trunk of his car for the trip to his Bethesda home. "Everything has been confusion," she said, as she maneuvered in a walker toward her brother's car.

"I don't remember heat like this except in Alabama and Georgia, when I was in the Army," her brother said. "There you sort of get used to it. This hit us too soon."

There were other close calls.

District fire officials said the heat indirectly caused minor fires at a single-family home in Northeast Washington and in a brick apartment building in Northwest Washington. The fires started when air conditioners attached to flimsy extension cords overheated and set objects nearby on fire.

Air conditioning was a precious commodity throughout the mid-Atlantic region, particularly yesterday, as temperatures soared to their highest point this week and workers returned to offices after a three-day holiday weekend.

The demand placed tremendous stress on the power grid that serves Washington and Maryland, as well as Pennsylvania and New Jersey. Pepco officials said peak-hour consumption exceeded the 5,800-megawatt record set June 26, 1998. One megawatt hour is enough to power a small town's electricity for an hour. Virginia Power officials and Baltimore Gas and Electric Co. also announced record use.

The consortium of regional utilities, known as the PJM Power Pool, announced at 2:15 p.m. that it would reduce the amount of current running through a 500,000-volt line that distributes power through the three-state area. It is one link in the transmission chain that moves electricity along the East Coast.

The huge demand for power also was reflected in the open market for electricity, which utilities use to buy and sell power among themselves. Usually a megawatt hour of electricity costs $20 to $25. At noon yesterday, the price was a staggering $940.

Pepco officials warned that if consumption did not decline soon, they would begin unplugging neighborhoods from the power grid at roughly 40- to 50-minute intervals. That would lessen the likelihood of the system crashing at any one point.

To keep up with consumption, Pepco ran its six generating plants at full capacity yesterday, burning almost twice as much coal as an average day and turning on 34 less efficient gas turbines reserved for only the busiest days.

The plant along the Potomac River in Alexandria has half as much coal on hand -- 50,000 tons -- as it usually does because of the high demand for power this year. Bulldozers worked quickly to move 4,500 tons of coal from 75-foot-high mounds during the day yesterday. The fuel traveled by conveyor belt to the boilers, where it is burned to make steam. The plant shrieked with the noise of giant turbines.

Out in the field, utility workers repaired hundreds of blown fuses, overheated by the steady use of air conditioners that have not rested for days. Bill Gausman, Pepco's general manager for power distribution, said he refused requests from New Jersey and Pennsylvania utilities for help replacing hundreds of blown transformers and fuses because "we're experiencing the same situation here."

Shortly after 11 p.m., Pepco spokeswoman Nancy Moses said about 3,000 customers were without power in the District. About 300 customers lacked electricity in Montgomery, and 80 were without power in Prince George's County, she said. The scattered outages were caused mostly by blown fuses on utility poles that had become overwhelmed by neighborhood use. Twenty-one crews will work around the clock to restore power, she said.

"It's about average, normal, in comparison to extreme weather conditions," Moses said. "During this kind of heat, we usually have a few thousand to a few hundred [customers] without power. We have it in very hot weather and very cold weather."

In Northern Virginia, 102 customers were out of power, a Virginia Power spokesman said. Those outages were mostly in Alexandria, Springfield and Herndon, he said.

In Fairfax County, two houses reportedly were struck by lightning about 9 p.m., but neither sustained serious damage. One of the homes appeared to have been struck in the chimney and filled with smoke but did not catch fire, officials said.

Yesterday's 103-degree temperature broke by three degrees the Washington record for the date set in 1977. The all-time high temperature recorded for Washington was 106 degrees, set first in 1918 and then again in 1930.

National Weather Service forecasters predict some relief today as dry air from Canada sweeps in from the Northwest, driving out lingering humidity and dropping temperatures into the low 90s. Utility officials hope it will provide at least a temporary respite.

That won't come early enough for some tourists who sought shelter in the shadows of the monuments, including members of a Florida family who said they had never been so hot in their home state.

"It's the full outdoor experience," said David Jacobs, flashing a smile beneath a moist straw hat. He and his wife, Melissa, traveled with their two young daughters from their suburban Miami home to see the monuments and hit the summer's hottest weekend.

"Believe us," said Melissa Jacobs, "we were surprised."

Staff writers Sewell Chan, Steven Gray, Spencer S. Hsu, Tom Jackman and Ann O'Hanlon contributed to this report.

CAPTION: Two Montgomery County rescue workers, Cleveland Evans and Lt. Jeremy Gruber, right, evacuate Clarice Haudenshield from Leafy House, a high-rise senior housing complex in Kensington whose air conditioning failed.

CAPTION: A bulldozer moves coal in the storage yard of the Potomac Electric Power Co. generating plant in Alexandria.

CAPTION: Pepco workers sweep up around the power plant's boilers. Power consumption in the Washington area yesterday reached record highs.

CAPTION: Robert Waugh, of Orange County, Va., takes a break from his job moving a gas line as part of construction work near the Springfield interchange.