Washington baked and broiled in 90-degree temperatures again yesterday, but area residents breathed easier as the first air pollution health advisory in two years was canceled.

The huge hot air mass that has roasted the city for days remained relatively immobile, weather forecasters said, but enough of a breeze nevertheless arose to dissipate the accumulated dirt in our atmosphere.

After two days of inhaling air officially adjudged "unhealthful" Washington breathed air yesterday that was far less contaminated with ozone and was formally termed of "moderate" quality.

In addition to the breezes that blew away what pollution was produced, there appeared to be less automobile traffic producing it here yesterday, according to National Weather Service forecaster Harold Hess.

Ground-level winds of up to 16 miles an hour with gusts as high as 25 did much to clear away the haze that had hung over the city. But they did little to end the monotonous reign of 90-degree heat, which continued for the 21st day this steamy month and 47th day this sweltering summer.

Last month, the hottest in Washington weather history, the thermometer boiled to 90 or above on 21 days, matching an all-time record. That record was matched again yesterday, and with no real relief in sight, could be broken today.

Yesterday's high temperature was 96 degrees, recorded at National Airport at 3:56 p.m. Today's high is expected to be between 92 and 97.

Meanwwhile, the U.S. Geolgical Survey said preliminary statistics indicate that Washington took more water from the Potomac River this month than ever before.

Experts said it appeared that about 373 million gallons a day was taken, about seven million gallons more than the previous record, set in July 1974.

Despite the heat and the impressive statistics, there was no sign that Washingtonians were drinking the river dry. Average daily flow was about 2.6 billion gallons, about seven times as much as was used.