After teasing working Washington with a week of crisp sunshine, the fickle forces that control such things turned on the weekend city yesterday, delivering a heat-bloated day more suited to a summer swamp than a springtime capital.

Making for what the National Weather Service said was the most uncomfortably humid day this year, the temperature rose to 86 degrees, with the relative humidity at79 percent.

The heat was squelched in mid-afternoon by a thunderstorm that blew through this area with winds of up to 54 miles an hour. The temperature fell 15 degrees in a less than an hour as up to an inch of rain was reported in some suburbs. Local power companies reported temporary, widely scattered power outages, primarily in Fairfax and Montgomery counties.

Today's weather is expected to be cooler, with showers likely. Temperatures should be in the upper 60s, with a 40 percent chance of rain, according to the weather service.

Yesterday's swelter and squall, however, seemed to have little effect on those determined to go outside and play. Thousands of people descended on the Mall to play volleyball, softball, polo and Ultimate Frisbee. Others simply lay in the pre-storm sunshine and perspired.

On the waterfront, the heat and gusty winds did not stop the Fifth Annual Parade of Boats and Blessing of the Fleet.

"Be attentive, O Lord, to our supplications," said Father John Way of St. Dominic's Church, who stood on the bow of a 72-foot cruiser, facing a parade of nearly 200 boats in Washington Channel, "and bless this ship and all who sail hereon, as you blessed Noah's ark in the deluge."

Way, dressed in clerical black with a purple stole around his neck, said that this was the second time he had been asked to bless a fleet of 200 or more boats.

He had prepared well for the ceremony. His prayer was typed on a thick note card that did not flutter in the breeze, and he carried the holy water in a small plastic bottle that enabled him to squeeze it out with one hand. Of the holy water, Way said: "I just throw it in the general direction of the boats."

The Rev. Jeanne McKinzie, of Westminster United Presbyterian Church, also invited to bless the fleet, prayed: "We praise and thank you for those who work on the waters, whose labors bring food to us or serve our common human community."

While eloquent, the prayer may not have been all that applicable to the yachts and cruisers passing by. The work on the water yesterday, aboard such vessels as the former presidential yacht Sequoia, appeared to consist chiefly of downing cool drinks while waving happily to the crowd ashore.

On Capitol Hill, in a ceremony that marked the start of National Police Week, an estimated 500 people honored the 162 police officers who died last year in the line of duty. Members of the ladies' auxiliary of the Fraternal Order of Police placed a wreath of 162 white carnations in the Senate Park on the north side of the Capitol.

Near the Lincoln Memorial, on the polo field along Ohio Drive, the afternoon provided a wilting opportunity for polo ponies and their riders to get in some pre-season work.

Rahman Abbar, 30, from Saudi Arabia, worked out his six polo ponies. Between chukkers, as the 7 1/2-minute periods of play in a polo match are called, he sat in a lawn chair beside the field and told how polo has captured his heart.

"This was a game that impressed me," said Abbar, who is a third-year law student at Georgetown University. "I heard that kings and queens played it. To tell you the truth, that's why I went into it. On the outside, it is glamorous. But now that I am on the inside, it is a disease."

To improve his game, Abbar said, he bought ten horses from Argentina at a total cost of $10,000 and flew them north. He was about to explain how he can afford to play high-stakes polo when he was called for another chukker.

As the sky turned black with thunderclouds and rain began to fall, Abbar scored a goal.