"What do you think of a man my age on a motorcycle?" laughed Joseph Street, 62, a retired U.S. Park policeman-turned insurance salesman as he straddled his gleaming purple Harley 1200cc hog yesterday afternoon and prepared to roar about Rock Creek Park on a glorious, blue-sky afternoon.

"The image is that brains and motorcycles don't go together," said the self-described "pseudointellect" who annoints his chrome with Windex, his paint job with Blue Corral and softens his cycle seat with saddle soap. "But the image is changing -- like the weather.

"It's an ideal Saturday afternoon -- people aren't racing around punching the clock or pushing to make deadlines or rushing home . . . "

Indeed, it was a day of celebration for thousands of Washington area residents who flocked to monument grounds for the music and politics of Advisory Neighborhood Council Day, launched their sailboats in the breezy Potomac, played volleyball, pedaled bikes about the byways, unfurled their kites and jammed Rock Creek Park for its 89th birthday party.

Even as the dawn broke over dewcovered lawns, christening it, at 60 degrees, the second coolest day of the season, the weather heightened the senses, making leaves seem greener, joggers sweat less and enjoy the pain more and, according to U.S. Park Police, helping keep runaway tempers in check.

A crowd U.S. Park police estimated at 7,000 poured into Rock Creek Park -- in cars, on foot, on bikes -- to sample the exotica of international dancers, snap up trinkets for sale and nibble tasty tidbits from 22 countries. Wisps of cloud moved across a blue horizon and Jeanne Calderon, a lawyer out for a stroll with her husband, pronounced it, "A day that makes you glad you're in Washington."

"The weather makes me a little homesick," said Mun-kyou Chae, 40, a Bank of Korea official here for a government training program who took a deep breath and opined that "it's just like Seoul this time of year."

Next to the Liberty Bell outside Treasury, Hector Ribeiro, 35, a Uruguayan trainee with the International Development Bank, prepared to snap a picture of his wife, Mirtha and their daughter, Virginia, and said, no, the weather was just like his hometown, Montevideo.

Everywhere, it seemed, tourists and residents claimed the beautiful day as their own. It was the kind of day politicians would have tried to take credit for if only they could have.

Even though evidence of Tropical Storm David's wrath remained throughout Rock Creek Park -- trees axed in two, bridges still closed from torrential flooding, silt and sand covering much of the creek bank -- Washington area residents like Robert Yerman and his wife, Ann, were not deterred. "It's just a pleasure to see no rain," said Yerman, an accountant who packed his 1-year-old daughter, Leslie, on his back.

"That's enough!" gasped modern dancer Brian Walker, 28, as he collapsed, out of breath (but to applause) with his partner, Salma Rahmhan, 23, after throwing himself gracefully about the stage in back of Pierce Mill to the Afro-Brazilian rhythms of a tape deck. He hails from Trinidad, she from Rio and their rhythmic gyrations were all part of Rock Creek's birthday celebration. "I didn't think it would be such a grand affair," he said.

All Toon, 23, a Red Cross emergency medical technician, took time out from his box of doughnuts to treat 20 cases of bee stings. "Actually," he said, "most were yellow jackets. We apply Sting Kill and wait to see if they go into shock. If they do, we take them to the hospital."

No one went into shock yesterday. Nor, he said, did they have to treat any cases of heat stroke.

Gusting winds kept Kevin Doeppelman's hot air baloon in check until late afternoon across the street, but Dave Lanier sat under a tree and said he didn't mind. It was his birthday, too. He was 49.

"You're an old dude," snickered Tony Jenkins, 41, a D.C. public school official. "I don't know what I'm doing hanging out with you."

Lanier, a design professor with the University of the District of Columbia who was resplendent in a brown Stetson, brown boots and brown tinted sunglasses, tethered his two miniature poodles, Angie and Pele, and took a long drink from a paper sack, a beer. He felt like crawling into a cave during the summer, he said, and, since he was a "cold weather cat," he considered the weather an auspicious sign, it being his birthday.