The Junk Yard Band turned lunch hour yesterday at McPherson Square, normally a preserve of well-heeled professionals sipping unfiltered apple juice, into a frenetic display of "Junk Folk," the latest craze in urban street music.

Hundreds of people wriggled with glee in the park at 15th and I streets NW, as office workers in shirt sleeves warmed up to springtime. The band's members, who range in age from 12 to 18, slapped away at crates, cartons and trash-can tops in the glimmering sunshine.

"This music is just too cool to avoid," said Derrick McCrae, the band's manager, as he walked among the listeners, collecting donations in a gray plastic garbage can. "Even a clone would go crazy over it."

The band and its listeners were not the only ones going crazy. Traffic snarled and crawled along Independence Avenue as drivers headed toward momuments and malls. By 3:30 p.m. the temperature had reached 83 degrees at National Airport, just short of the record high of 86 for this day, set on April 5, 1910.

But National Weather Service forecasters said that the balmy weather would not hold, with the forecast calling for thunderstorms and temperatures dropping into the 60s by late last night and for much of today as a cold front moves in from the south.

As thousands of area residents prepared for the weekend's holidays, forecasters warned that time was running out to view the city's cherry blossoms. They said that high winds gusting up to 30 miles an hour along the Potomac could leave the fragile blossoms mostly on the ground.

At the Baskin-Robbins Ice Cream Shop on King Street in Alexandria, some must have worried that the ice cream would run out.

"This just doesn't happen. It's not even 11," said Janellen Wolf as she watched a line stretch out the door of the shop yesterday morning. Wolf, looking harried in her candy-striped uniform, had been scooping ice cream for more than an hour.

Frazier Coleman, a mail carrier in the District, seemed to have the right job for this kind of a day.

"I know what they say about snow and sleet and the mail getting through," he said as he walked down East Capitol Street, patting babies on their heads and talking with mothers in the neighborhood, "but this is why I took the damn job."

If the fine weather brought pleasure to thousands who enjoyed the breezes flowing from the south, others treated spring fever as if it were a crippling disease.

"Look at those people out there," said Vince Lofton, surveying hundreds of loiterers jamming the streets that he usually speeds through as a bicycle messenger. "They don't want to move, they don't want to work, they don't even really send messages on a day like today. They're just in my way. I wish they could all go back to the office."

Theories vary as to why Washigton gets so excited about its gentle spring. Some say it's not because of the fields of flowers that burst across the region, or their soft fragrances, but because summer's deadening heat soon will strip all pleasure from the sunshine.

"This is all we have," said Michelle Provost as she sat in Lafayette Park with a friend. "Winter is so dreary, and summer is so overwhelming that, when April hits, you just want to tear loose."

Of course, tearing loose is what spring is all about. Crowds streamed to local airports yesterday, racing to spend the Easter and Passover holidays with friends and family.

But perhaps nobody in the region did springtime's bidding with greater dedication than Robert Brandt of the District.

Having had a "tough time" with his girlfriend recently, Brandt made a big play to win her back. He took a 75-foot banner and unfurled it on the steps of the Capitol.

"Happy Birthday, Cindy. I Love You," it read.

"I suppose it's spring," replied Brandt when asked why he did it. "But you really have to be in love with a girl to to this."