Thousands of Northern Virginia schoolchildren were sent home early yesterday afternoon as an August-like heat wave sent temperatures in Washington to 95, breaking a 15-year-old record for the day.

While many schoolchildren in Fairfax, Prince William and Arlington counties were granted a reprieve from academics, some area workers weathered the heat better than others.

"The weather? I'm an ice cream man. It's lovely," said Austin Wiles, a Baskin-Robbins delivery man with vanilla hair and chocolate-colored trousers. "I just go from the refrigerated truck to air-conditioned shops."

Many others, including Randolph C. McLeod, said yesterday's 95-degree heat and 50 percent humidity was anything but welcome.

"It's about 400 degrees near the hickory pit barbecue," said McLeod, the cook at O'Brien's Pit Barbecue in Rockville. McLeod said lunch business, which usually picks up after Labor Day, was slower than usual yesterday. "It's just not a day for chili and barbecue."

The National Weather Service announced that Washington's official temperature, recorded at National Airport, hit 95 at 2:18 p.m., one degree higher than the record for the day set in 1970. And weather service meteorologist Earl Laws said there was no relief in sight.

"It'll continue the same, into the mid-90s, until Friday," said Laws. Moreover, he said, the humidity, which registered about 50 percent yesterday, will increase each day.

School officials in Fairfax closed all 157 public schools and sent the county's 125,000 students home one hour early because, they said, the temperature had become unbearable in many schools. In Arlington, four schools without air conditioning closed at noon and in Prince William, 12 public schools closed before 1 p.m.

No Maryland schools closed early yesterday, but Montgomery County officials said they will close the county's public schools one hour early today in anticipation of this afternoon's predicted heat and humidity.

Fairfax school spokeswoman Dolores Bohen advised parents to listen to the radio and television today to determine if Fairfax schools will again close early. "Since the weather tomorrow is predicted to be worse than today," Bohen said, the schools could close early again.

The Fairfax school system, like many other area schools, have no set formula, or maximum and minimum temperature, which automatically decides school closings, said T. Page Johnson, a school administrator.

Page said the system's four area superintendents consult with principals and, after assessing individual schools' temperatures and working conditions, report to Superintendent Robert R. Spillane, who makes the final decision.

Page said that "only very oppressive conditions" force an early closing in Fairfax because officials realize that both parents work in many families and their children have empty homes to go to.

Virginia Power and Potomac Electric & Power Co. spokesmen said the power demand was not expected to hit a peak. However, they said, if the temperature remained in the 90s until the weekend, a record power demand is possible.

Virginia Power spokesman James Buck, said the company's 1.5 million customers use 7,500 to 8,000 megawatts of electricity on a typical summer day. Yesterday Buck said air conditioners pushed the demand to about 9,400 megawatts.

Washington's September highs average 80.1 degrees, the weather service said. July's average high is 87.9, and August's is 86.4.

"Every year, I think after Labor Day it will cool off," said Stephen A. Fraver, a Postal Service letter carrier in Alexandria. "But it doesn't. It's just as lousy as August." CAPTION: Picture, Construction worker Tom Parker gulps water in midst of helping to build house in Reston in yesterday's 95 degree heat. The $250,000 house, to be built in 72 hours, will raise money for charity. By Wayne Partlow--The Washington Post