There was a sky blue as eyes over Roosevelt Island, and it was a perfect day yesterday for a walk along a path dappled with sunlight and stippled with crickets, hung with fiber optic cob webs.

It was a strange sort of day, slow and languid, sadly sweet. Neither hot nor cold, neither summer nor fall. Just an August day floating between seasons like a yellow leaf on the still water that hugged the island's edge. A day, said Crystal Hawthorn, 26, that "sort of spaces you out, like you're here, but you're not.

"Like when you were a kid and it got to be August. You knew you were going back to school again soon. I mean, you looked forward to it and all, but it was like summer is vacation and fall is going back to work," the key-punch operator from Arlington continued.

"It's like you want a change but you don't want a change at the same time. You know what I mean?"

Eighty-one degrees, 37 percent humidity, and the people were out, bicycling and playing tennis and carrying styrofoam coolers between one another, paying their outdoor homage to a beautiful day. But everywhere there was a tendency to downshift and glide. Bikers walked their bikes along Rock Creek Parkway, and joggers sat, chewing on weeds or talking.

In Adams Morgan, people seemed content to stare from their stoops in silence, and on the Potomac, a man paddled a red canoe while a woman in the bow read the Sunday funnies.

On Roosevelt Island, the statue of Teddy himself looked stern and bronze as ever, but Park Ranger Phillip Jenny, usually an energetic man by his own description, was sitting quietly in the shade, knees crossed and legs rubbery, waiting but not anxious to lead his 2 p.m. nature walk.

"I don't know, just don't have much energy today," Jenny said. "I guess all that heat and humidity kind of sapped me. I'm just being comfortable today . . . "

The day coming near the end of summer, some people felt less of a need to go outside at all. In the main reading room of the Library of Congress, Sidney Katz, 31, was bent over the May-June 1983 edition of "Overseas Timetables," checking Chinese train schedules.

Not that Katz, a Dupont Circle resident, was considering a trip to China. In fact, he had just returned from there. "I'm trying to figure out how I got between two cities I visited," Katz said. "Theoretically, there's no way possible to do it."

At the Corcoran Gallery of Art, Ellie Koch and Debbi McGlauflin were drawn to a William Wegman photographic exhibit. They came partly for Wegman, partly because it was too cold to swim, they said.

But it wasn't too cold for walking the paths of Roosevelt Island. It was a perfect day for a boy to drag his feet and kick pebbles at his sister, and for French bread, Bolla red and a serious discussion on a park bench, and for a man with his Canon and a woman posing on a foot bridge.

"You really can't complain about the weather," said Hawthorn. "You got to enjoy what's left of the warm weather. I like fall, but when you think about what follows, well, I'd rather not think about wearing a winter coat."