John Bisch idled at a traffic light near the Mall yesterday in his gold 1967 Camaro -- happy to be alive, happy to be outdoors on a sparkling Sunday afternoon, happy to be the owner of the day's most envied car: the convertible.

"This is freedom," Bisch, a 27-year-old Arlington accountant, said with satisfaction. "This makes driving fun."

Fun, in one form or another, was what most people had in mind yesterday as they thronged the Washington area's parks and monuments and enjoyed an afternoon of record-breaking warmth.

The mercury climbed to 78 degrees by 3 p.m., surpassing by 7 degrees the Washington area record for the date, 71, set last year, the National Weather Service said. The area's hottest day on record for the month -- 84 degrees -- was set on Feb. 25, 1930.

Up and down the East Coast yesterday, temperature records melted -- from the 80-degree reading at Roanoke to the 71-degree high in Worcester, Mass. Both cities experienced the highest temperatures on record for the month of February, not just the date.

Forecasters warned, however, that the balmy temperatures would soon give way to more routine late-winter weather. "Today should be the last day of really, really nice weather for a while, I'm afraid," meteorologist Dorothy Kropp said. "By the middle of the week, we'll be back to days when the highs are in the upper 40s."

Maybe so, but yesterday the multitudes lounging on park benches, playing golf, riding bikes or cruising in convertibles adopted a live-for-today attitude. "I'll enjoy it as long as it lasts," said Kenny Godfrey, 22, relaxing at East Potomac Park in his black 1981 Trans Am with its T-top open to the breeze. "How can you not be happy today?"

U.S. Park Police reported massive crowds and slow-moving traffic around the Mall. In Northern Virginia, Dorothy Werner, of the regional park authority, said that parking places were at a premium at Pohick Bay and Algonkian parks.

"Everybody is launching boats, picnicking, lying in the sun," Werner said. "We still had our picnic tables stacked up against trees for the winter and they've taken them down to use."

Owners of convertibles took the tops down this weekend for the first time since the unseasonably warm days of December and reveled in optimum convertible weather: a gentle breeze, low humidity, not too much direct sunlight.

They cruised in low-slung Corvette Stingray convertibles and brightly colored Volkswagon convertibles, MGs, Fiats and the occasional vintage Mustang. They refused impulsive, half-serious offers from strangers who wanted to know how much money they would take for their cars. They gave testimony to the comeback of the convertible as the romantic vehicle of the '80s.

And they exhibited the style -- cool, relaxed, carefree -- that seems to go automatically with driving a convertible. Convertible owners, for instance, never grip the steering wheel; they lightly drape one arm across the top with the other elbow usually propped on the door. Thirty-five mph is the best speed. Sunglasses are a must.

Jeff Constantz and Faye Ferguson were a sporty couple in their sunglasses and casually ruffled hair, pulling out of East Potomac Park at afternoon's end in Constantz's 1965 maroon Mustang convertible.

"There's a definite uplifting of the spirits when I drive this car," said Constantz, 25, a banker.

"It's sexy," added Ferguson.

Ken Levell and Ron Hinton agreed that Hinton's robin's-egg blue Volkswagon convertible is helpful as a opening topic of conversation. "People -- and I mean by that, women -- notice us more," said Hinton, 28. "We're just more visible. Everybody wants to ride with us.