A stretch of unusually pleasant August weather ended in a blast of records yesterday.

The temperature reached 100 degrees, one degree higher than a mark that had stood since 1948 at National Airport and four degrees higher than a seven-year-old record at Dulles International Airport.

Yesterday was an uncomfortable reminder that summer still has a way to go. Perhaps because of humidity levels of 50 percent or less, though, many Washingtonians seemed unaware of how hot it was.

"I thought it was about 85," said Carolyn Woods, a secretary at the National Mortgage Bankers Association downtown.

"Maybe because the wind was blowing."

"It didn't hit 100, did it?" John Bixler, assistant director of the bankers association, asked in disbelief. "Everyone came in the office and said it was brutal outside. I said, 'I'm staying in.' "

Yesterday's high was a sharp rebound from unseasonably cooler temperatures that in the last week had ranged from highs in the mid-70s to lows in the 60s.

Normal temperatures for this time of year are 85 at the high end and 67 at the low end, said National Weather Service forecaster Bob Oszajca.

The low of 58 degrees on Monday at National, though, fell far short of the record 49 set in 1890.

For John Bixler, usually a dispatcher for Apple Courier Co., any kind of hot was too hot.

"I've been sitting in an air-conditioned office and didn't know," said Bixler, who was forced yesterday afternoon to fill in for another employe and make a delivery on bicycle. "Right now, I'd just like to get back to the office. I wish it would rain."

Bae Suckdoh, a sidewalk jewelry vendor at 15th and K streets NW, agreed.

"Right now, it's not so bad," said Suckdoh as he packed up his wares to go home late yesterday afternoon. "But between 1 and 2 o'clock, it was too hot. I can't stand it."

The scorcher should be brief, according to Oszajca. Temperatures today are expected to vary from the low to mid-80s, continuing through tomorrow, with a chance of showers or thunderstorms. It is supposed to get cooler again on Sunday.

The summer of 1987 will be remembered for weather charts spiked with repeated temperature readings on the high side, beginning in July when a a 24-day total of 90-degree days was without precedent.

The heat and lack of rain continued to wear on surrounding farmers.

In Virginia, 22 counties had asked to be declared disaster areas as of yesterday, and state officials continued to assess the damage to crops.

In Maryland, Gov. William Donald Schaefer has requested federal disaster aid for 15 counties.

Still, officials said the damage is not likely to be as severe as last year, when drought severely affected farmers throughout the Southeast.

Oszajca said the weather in the Washington area was affected by a high pressure system that passed north of here, first bringing cool air from the Great Lakes, followed yesterday by warm, moist air from the South.

Relief will come, he said, from a cold front approaching the area from the Northwest.

But, as they say in baseball, it's not over till it's over. Summer does not officially end until 9:45 p.m. Sept. 23.