It was high noon yesterday, and Craig Schroeder watched the instrument panel, rooting for the mercury to rise two more degrees.

"Aw, come on," he said, coaxing the thermometer. "Hit 90. Hit 90." He sat back in his chair, lit a cigarette and tapped the glass that registered 88 degrees. "It's trying," he said apologetically. "It's definitely trying."

While the rest of Washington sweltered during a record-tying heat wave -- not since 1872 had the city endured 18 straight days of temperatures in the 90s -- Schroeder was not satisfied. He wanted to go for the 19th

For the 26-year-old official weather observer at National Airport, yesterday marked the last inning in the world series of Washington weather. For him, breaking records is not everything -- it is the only thing.

The tension was mounting -- 89 degrees. Schroeder chewed his nails and watched the instruments. At 12:20, the red needle fluttered once, but stayed at 89. At 12:21, it fluttered again. Schroeder eyeballed the panel and sucked in his breath. "You got it!" he said. "There you go, 90 degrees."

There was no champagne. No brass band. No cheerleaders. There was just Craig Schroeder, sipping coffee from a "CRAIG" mug, secure in the knowledge that yesterday -- hot, muggy sticky yesterday -- would go down in the history books.

"When you break a record in Washington, it's really something," he said, "because the records go back so far."

In his customary uniform of blue jeans, mustache and a shock of frizzy hair, Schroeder pulled out a worn notebook from the desk in his tiny cubicle near the airport's control tower. "Look at these dates," he said. "They go back to the 1800s."

Keeping records, he said, is comforting to the general public. "People know it's hot," he said, "but people want to know how hot it is."

The high temperature yesterday was 93 degrees. The weather forecast for the rest of the week calls for cooler temperatures with a chance of thundershowers each day. For Washingtonians, it means relief. For Schroeder, it marks the end of a winning streak.

"There's an outside chance we may go for the 20th day in the 90s," he said. "But today was the big day."

As official weather observer, Schroeder monitors Washington's temperature, barometric pressure and other weather data. Every hour, he sends the information via a Western Union teletype machine to newspapers, radio and television stations, the telephone company for their recorded weather message and the National Weather Service in Suitland, Md.

"I sorta always liked weather," Schroeder said. "And this is an important job. People have to be informed on what's happening outside. I take a lot of pleasure informing them."

The job does have its occupational hazards. Several weeks ago, while walking on the observation deck four stories above the runway, Schroeder was caught in a thunderstorm. "A gust of wind blew me clear across here," he said. "I rushed back inside and the wind was registering 80 miles per hour."

A teletype machine clattered in the background. Schroeder read the wire. "Dulles 86, Richmond 88, Baltimore 85. Looks like we're the hot spot," he said.

Schroeder said weather service employes like to bet on the whims of Mother Nature -- when the high temperature will hit, what the cloud ceiling will be and other trivia. "But not me," he said. "I'm not allowed to bet. I'm the one that has to monitor it."

Schroeder answered the phone. The caller, he said, wanted to know if the record for "highest lows" had been broken. He checked the notebook. For the last 18 days, the mercury has not dipped below 75 degrees. "I don't know whether that's a record or not," he said. "I'll have to find out." By late yesterday, though, he still hadn't finished his research.

The weather observer relaxed in his chair. "There's something else interesting going on," he said. "We've had five days with temperatures in the 100s. That's second only to the record set in 1930 when they had 11 days in the 100s."

That means only six more sweltering 100-degree days to tie the record, seven to break it. Although Washington might not be up for the challenge, Schroeder is. Breaking records, he said, "is neat."