For the second straight day, Mother Nature did a meteorological flip-flop with record-breaking warm weather here and elsewhere as shirtsleeved sun worshipers cycled, jogged, sailed, walked and generally luxuriated in springlike temperatures.

It was a beautiful day for a June wedding. As she posed for post-ceremony pictures on the steps of St. John's Church by Lafayette Square, Sherri Walker, nee Massey, held a red, green and white bouquet that looked decidedly unseasonal despite the Christmas motif.

"This is idyllic for a wedding," said Kathryn Walker, the mother of the groom, who left the fur she brought from Akron, Ohio, in her hotel room. "We expected to come to snow and ice."

The official thermometer hit 75 degrees at Washington National Airport, shattering the old record of 64 degrees for the day set in 1893 and tying the highest reading ever recorded for a day in December. That day was Dec. 28, 1946.

Temperature records tumbled in 70 other cities throughout the eastern half of the nation with all-time highs ranging from 80 degrees in downtown Baltimore to 71 in Kansas City. New York City's Central Park, where people had been sledding just two days ago, melted under a record 70 degrees.

With the warm sun and spotless blue skies of yesterday, Washington residents may have forgotten that almost exactly one year ago, they were shivering in record-breaking cold. Temperatures fell to record lows of five degrees and three degrees above zero on Christmas Eve and Christmas Day, bursting pipes, freezing traffic lights and leaving at least three persons dead. The extreme cold abated slowly with below-normal temperatures persisting into the new year.

In contrast to those freak conditions, National Weather Service forecasters say this week's warm weather will persist today, with another possible record high temperature, and then begin tapering off tonight. Lows are expected to fall into the 40- to 45-degree range tonight, according to forecaster Bob Oszajca, with a 40 percent chance of rain Monday and highs only in the low 50s. Tuesday's outlook, he said, calls for partly cloudy skies and near-normal temperatures in the 40s.

Throughout the Washington area yesterday, the scene was more summer than winter. Joggers, cyclists and assorted tourists jammed the Mall and museums downtown. Shirtless sunbathers sprawled on the grass near the Smithsonian castle. Trash containers spilled over with hamburger wrappers and styrofoam cups from the crowds. Children in shorts poured into playgrounds from Gaithersburg to Manassas. The thwack of tennis balls echoed across neighborhood tennis courts.

Ken Towe surveyed the back nine at the Belle Haven Country Club in Alexandria and made his pronouncement. "It's a zoo," he said, swinging his bag of clubs into a waiting golf cart.

Then why bother playing? "You don't get to say 'Happy New Year' on the golf course around here very often," Towe said before driving off with the rest of his foursome.

Inside the clubhouse, assistant pro Marty O'Rear was juggling tee-off times with the precision of an air traffic controller. "They started coming in at 7:30 and they've been coming ever since," said O'Rear. The traffic, he said, was about three-fourths that of a busy summer Saturday. "And that's probably only because the day is shorter," said O'Rear, who -- alerted by weather forecasts -- started dragging golfcarts out of storage yesterday and filling sagging tires.

Deborah Jackson had expected to be "folded in front of the fireplace, watching the football game." Instead, Jackson left her husband at home doing exactly that, picked up her tennis racket, and headed to Fort Washington National Park to get in her first volleying since late October.

Jackson's partner, Pearl Allen, was taking the July-in-Christmas bit slightly further. "I even plan on grilling some hamburgers when I get home," she said. "I've never done that in December."

In another corner of the park, Randy Taylor and Ed Reams had their shirts off, their tape deck blaring, and their frisbee ready to fly. "This'll probably be the last day we'll get out" to play frisbee, Reams said. "Of course, I've said that about five times."

By noon, hundreds of tourists ringed the Washington Monument, waiting up to an hour and 10 minutes for the elevator ride to the top.

"On an ordinary winter day, we would have strictly a walk-in crowd . . . maybe 15 or 20 people," said National Park Service ranger Cathy Bowman. But yesterday, she said, Park Service officials expected 3,000 visitors, the same number that showed up Friday.

"If it was normal winter, people would be huddled up," Bowman said. "They couldn't stand here for an hour."

What the Washington Monument gained in attendance amounted to a loss for the two open-air ice skating rinks downtown.

The Pershing Park rink on Pennsylvania Avenue NW near the District Building was shut down, its surface an empty moonscape of gray slush.

The nearby Sculpture Garden rink at Seventh Street and Constitution Avenue NW remained open, but the few skaters there had to negotiate through a half-inch skim of water as well and deck chairs placed over especially bad spots. The rink's refrigeration system battled the sun throughout the day, "and we've managed to stay open," said rink manager Michael Garner. " . . . A lot of people are calling in wondering if we're open."

Out in Northeast at the U.S. National Arboretum, scores of visitors swarmed over the rolling hills as attendants fussed over shrubs that were beginning to bud.

"People are showing up in halter tops and shorts. It's great," said Dan Chiplis, horticulturalist and assistant curator of the arboretum's bonsai garden. "On a typical cool, drab winter day, we average maybe 30 or 40 visitors in the garden, but today we'll get 200 to 300."

Chiplis held the delicate branch of a Japanese full moon maple, pointing to newborn buds swollen by the warm afternoon sun.

"It's not serious yet," he said, "but it's hard to say at this stage. . . . Some of the cherry and forsythia plants may have their buds blasted if there's a sharp drop in temperature."

Sidewalk restaurants sprouted tables and customers. The American Cafe on Massachusetts Avenue NE near the Capitol moved indoor tables out to its brick patio, while next door at La Brasserie, manager Tom Cannon beamed at his outdoor crowd. "It's unusual this late in December to have outside tables," he said. "We're usually closed outside by mid-November."

At Rumors restaurant downtown, all 10 outdoor tables were filled. Donna Dooley of Falls Church, lunching alfresco on tuna salad, said, "It's terrific. We've got a little bit of Florida right here."

Standing at the entrance to Burberrys on Connecticut Avenue, manager W. Blaine Sharpe looked slightly forlorn, his store nearly bereft of customers, and trade in Burberrys trademark cashmere scarfs and lined overcoats slowed to a trickle.

"Foul weather is our friend, and we haven't seen much of it lately," he said. "If it were 40 degrees cooler, we would be much better off."

Sharpe was not alone in his plight. Despite an abundance of after-Christmas sales, area merchants reported that customers had abandoned the malls for The Mall. "Normally, Saturdays are crazy," said Tina Strickler, glum at the prospect of spending the day behind the counter at Bloomingdale's men's department in Tysons Corner. "It's not completely deserted here, but I've seen better," she said.

Water, on the other hand, attracted considerable crowds -- or, as U.S. Park Police helicopter pilot Butch Cronin phrased it, there was "very heavy visitation on both sides of the river." At Thompson Boat Center in the District, Bob Earle and Whitney Azoy set off down the Potomac in a two-person kayak. Across the river at the Washington Sailing Marina, Phil Seiser and Bob Laughlin took their 16-foot sloop off the dry slip and out for a spin. Looking out at the river, Seiser said, "Today it's just . . . "

"Perfect," Laughlin interrupted.

But the day did not shape up quite so well for David Freeman of Arnold, Md., who was climbing on the rocks at Great Falls. Freeman made his way across a fallen tree to one of the small islands on the Maryland side of the river, when the U.S. Park Police spotted him.

The Park Police fished Freeman off the island with a helicopter and, after depositing him on dry land, presented him with a $25 ticket.