Washington baked and broiled yesterday under the fierce glare of a searing late summer sun that sent the mercury to 98 degrees, breaking a record for the date and aggravating the extended meteorological misery of one of the hottest seasons in the area's history.

Yesterday's unprecedented high temperature, reached at 1:25 p.m., matched that of the day before, which also set a record, and helped create one of the most tormentingly uncomfortable September weekends in memory.

With the mercury reaching 99 degrees at Dulles International Airport and 100 degrees at Baltimore-Washington International, it seemed that only the relative absence of humidity permitted survival under yesterday's oppressive conditions.

While today's forecast, calling for temperatures of about 90, seems to offer hope of relief from the weekend's fiery heat, the drop in the mercury may be earned at the expense of an increase in discomfort-provoking humidity, a National Weather Service forecaster warned.

"The moisture in the air is increasing, which will make it more difficult to warm up," said NWS meteorologist John Forsing. But, he added, "It'll probably feel just as uncomfortable."

Tuesday's temperatures may dip into the 80s, however, which would approach the normal range, and with autumn 10 days off, may suggest the possibility of ultimate freedom from this summer's ferocity.

Many Washingtonians, after completing a week of heat-caused school closings, took refuge in air-conditioned homes and buildings Saturday and yesterday as the mercury climbed quickly toward its record levels.

Reports that Saturday's 98-degree temperature broke a record of 96 that had stood for 86 years or that yesterday's high broke a record of 97 degrees that had been set in 1900 confirmed their determination to spend a sedentary weekend.

Others ventured outdoors anyway, and, some of them, with sweat-soaked clothing plastered to their backs, confessed that they regretted it.

"I should be home in my pool," Ron Firmani said from a booth at the annual Italian-American festival in Mitchellville yesterday. "This is incredible."

In placing the blame for the disagreeable weather conditions, weather service forecasters cite factors that include a high-pressure system off the Atlantic Coast. They also point to the arrival here of hot air from the Midwest at a time when the Washington area had enough hot air of its own.

In addition, said forecaster Larry Wenzel, the cool drafts of Canadian air that traditionally arrive here each summer just when things are beginning to become unendurable, have failed for the most part to show up.

As a result, this has been one of the hottest summers on record, with temperatures reaching 90 degrees or above on 51 days so far this year.

Yet, while Washington has certainly suffered, it has not been singled out to bear the brunt of summer's worst. Temperatures yesterday reached 100 degrees in Providence , R.I., and Wilmington, Del. It was 97 degrees in Norfolk, and 98 degrees in Richmond.

And despite the weather, and no matter what their reactions to it, thousands of people did turn out yesterday for the Mitchellville festival and for Adams-Morgan day in the District.

On Saturday, as temperatures soared in the late afternoon, other thousands consumed record amounts of souvlaki and gyros, placed their arms on each other's shoulders and danced the traditional Greek "Sailor's Dance" at the annual fall festival of the Saint Sophia Greek Orthodox Cathedral on Massachusetts Avenue NW.

Although the total rainfall so far this year has been higher than usual--33.1 inches, thanks to heavy spring rains--the Washington area is now enduring an unusually dry period. The last substantial rainfall was on Aug. 28. The forecast calls for only a 20 percent chance of showers or thunderstorms through Tuesday, Wenzel said.

The combination of heat and dryness has been devastating to area farmers. "The corn crop is almost nothing, the tomatoes are down, the beans have burned up, and the peppers are just wilting," said Bev Armentrout, who owns a farm in Poolesville and sells her vegetables at a stand on Wisconsin Avenue and Upton Street NW.

"We lost our first crop because of the floods in the early spring. We replanted and now the crops are burning up or not maturing because there's no rain," she said.

Lawns and gardens are also suffering. "I feel sorry for anyone trying to grow a lawn right now. Their water bills must be outrageous," said a spokesman for the Meadows Farms Nursery in Fairfax County.

"Water them, that's all you can do," said Ray Johnson, general manager of Johnson's Flower Center in Northwest Washington. Johnson recommended holding off on seeding new lawns until the weather breaks. "Water the area thoroughly three to four days ahead of time" because the soil is so dry, he advised.