A blast of oven-hot air sweeping through the Northeast cooked up record temperatures in the Washington region yesterday, prompting local utilities to purposely cut off power to more than 100,000 in the District and Maryland. Early evening thunderstorms knocked out power to another approximately 130,000 customers in the area, mostly in Northern Virginia.

Potomac Electric Power Co. and Baltimore Gas and Electric Co. initiated "rotating blackouts" of 15 to 30 minutes, which ended by mid-afternoon. High demand caused part of the problem, but the utilities also were hobbled because major power plants were out of service. It was severe thunderstorms, though, that caused the early-evening outages in Northern Virginia, parts of Southeast Washington and parts of Prince George's County.

Virginia Power, which held crews over from the day shift and brought in others from Richmond, was trying to have all electrical service restored by noon today, according to spokesman Aubrey Tarkington, who said outages ranged from Fredericksburg to Alexandria.

The damage to power lines in Northern Virginia, mostly from downed tree limbs, was called the worst since the late 1960s by Joe Martin, director of transmission and maintenance for the utility's northern division.

Early today, Virginia Power reported that 18,000 customers were still without power. Pepco reported that it had restored service to all but about 16,000 of the 40,000 customers who lost power during the storms. Most were in the eastern part of the District and central and southern Prince George's County.

Utilities reported electricity demand near an all-time high as three-digit temperatures were common throughout the Washington region. It was 100 degrees at National Airport, one degree short of the record for the day set in 1919.

It was 103 in downtown Baltimore, a record for the day in that city, and a record 99 degrees at Baltimore-Washington International Airport.

Flights at National Airport were delayed by the severe weather and an unrelated problem at the airport's interim terminal. A smoldering short in an electrical vault near the terminal's entrance caused about 400 people to be evacuated for about 20 minutes, acccording to airport spokesman David Hess.

National Weather Service meteorologist Ray Brady said relief should arrive today, with temperatures dropping to the relatively mild 80s. Utilities said the lower temperatures and emergency repairs at their plants should mean that blackouts will not be ordered today.

Besides cutting power, the late afternoon storms cut a swath of damage through parts of Northern Virginia, especially Fairfax, Prince William and Loudoun counties.

There was an avalanche of calls to the Fairfax County Public Safety Communications Center. "We were inundated," said Sam Keyes, assistant commander of the center. He said calls were for fires, water damage, lightning strikes, wires down.

"It's about the worst I've seen, and I've been here 18 years," Keys said. But he said little of the damage appeared to be major.

One exception was a fire started by lightning that destroyed a barn in Centreville containing seven cars, some of them antiques. Damage from the blaze in the 12000 block of Lee Highway was estimated at $300,000.

The power outages disabled traffic lights, and police officers took over at some intersections, punctuating their hand signals with shrill blasts on their whistles.

As sunlight and blue skies returned, many late afternoon shoppers found some stores operating with battery packs to power emergency lights and cash registers.

While the mid-week Fourth of July gave people the chance to beat the heat at beaches, swimming pools and back-yard barbecues, yesterday's high temperatures forced workers to find their own ways of coping.

At a construction site in Woodbridge, bricklayers inside an unfinished office park said they had the worst of both worlds -- no air conditioning and no wind.

"We're cooking right here . . . and it's getting hotter," said Bill Brack, "I just pour cold water on my wrists to cool the blood."

For the elderly and children, and those with cardiac problems and respiratory conditions, the heat was more than just wearying.

Although the air quality did not reach the level the federal government considers "unhealthy," it came close. Hovering in the 90 to 95 range yesterday, the ground-level ozone measured by the Metropolitan Washington Council of Governments did not quite reach the level of 100 considered unhealthful.

But there was a rash of vehicular heat prostration. AAA Potomac, which serves drivers in the District and suburban Maryland and Virginia, said service calls were above average. Usually, 10 percent of calls for emergency service are for overheating; yesterday they accounted for 30 percent of the calls, according to Betsy Glick, a public affairs specialist for the automobile club.

Around the region, people responded to the heat in different ways. At Dale City's Octopus Tanning and Toning, a tanning salon in Prince William County, 20 customers yesterday plunked down $7 to do under the lights what they could have done for free outside.

"Days like today we're busier because people don't want to be out in the heat," said co-owner Cindy Enke, who said that business had doubled.

Who's crazier? Those following a little white ball in the real sunshine "are nuts," Debbie Thomas admitted as she came off the 18th hole at Burke Lake Park in Fairfax County at midday.

"You've just got to be careful," said 18-year-old Shawn Spear, who was at nearby George Mason University, running up and down a grassy hill 36 times.

Spear, preparing for his first year of football at Randolph-Macon College in Ashland, Va., said "I'm going to take six breaks."

Common mortals, however, stuck close to air conditioners, fans and dark places. Outdoor cafes in downtown Washington were practically deserted. For Ashley Wiggins, the lone waitress assigned to the outside shift at the Ha'Penny Lion yesterday, the heat was shriveling her take-home pay. "I wasn't too happy about it," she said about her assignment. "I had to flip a coin with another waiter and I lost." said he's used to it. "I've been working outdoors all my life," he said. As Washington describes them, varieties of flowers are just like types of people, when it comes to heat.

"Chrysanthemums, carnations ... they hold up pretty well," he said. "But tulips, irises, freesias ... they're not so good. They're really delicate and they open up too quickly. The humidity takes the life out of them."END NOTES

Staff writers Valerie Chow Bush, Patricia Davis, Keith Harriston, Veronia T. Jennings, David Lindsey and Brooke Masters contributed to this report.