Evan Hughes took his lunch hour in the open window of a Walnut Street pizzeria yesterday.

"I think it's going to be ice-cold again," Hughes said, forecasting today's weather from his table alongside the nearly floor-to-ceiling window, which had been thrown open.

Well, maybe not ice-cold. But folks like Hughes - who decided "as soon as the sun came up" yesterday that he'd be dining out - weren't taking any chances.

The Rittenhouse Square resident was one of many who threw off their wraps and took seats by open windows or at sidewalk tables as the temperature chugged up. The National Weather Service said the high at Philadelphia International Airport was 65 degrees, rivaling the record 69 set in 1998.

Restaurateurs snapped to.

At Rouge, on the square, workers moved at least a half-dozen more tables outside. Business blooms wildly in warm weather, manager Reenie McDonnell said with a smile.

"We always have the one row [of tables]. We have heaters out there," she said, pointing to radiant-heat fixtures hanging above the row of tables permanently situated next to the outside wall of Rouge. And some were even occupied last week, when frigid temperatures plunged Philadelphians into reality.

Perhaps some nature lovers will huddle under those lamps next week - subfreezing temperatures are expected to return Sunday night, bringing a chance of snow.

Yesterday, even the fairest-weather alfresco diner found joy.

"I'm so happy," said Debra Felman of Center City, seated curbside at Rouge with pooch Pepper - who balks at going out in the cold - and friend Lori Pellegrino of Society Hill. "It's just so bizarre."

"We were actually at the gym and it was so beautiful out," Pellegrino said of how they wound up curbside.

"I hope my boss doesn't see me," said Bruce Cary, sitting several tables up the sidewalk. "I'm just taking a short break for lunch."

Added the Chestnut Hill resident, drawing chuckles from his two companions: "My office is here, which I'm about to go to and which I just came from."

John Morris hoped to capitalize on the spirit freed by the thaw as he stood outside Jean's Cafe, hawking Purple, a new antioxidant drink.

"They seem more happy when it's nice out," Morris said as he held out paper cups of Purple to passersby on the 1300 block of Walnut Street. "Everybody's strolling."

Still, as Evan Hughes reminded from the window of Pietro's Pizza, "This is an exception, really."

Toward the end of the lunch hour, the wind had picked up and cast doubt in the minds of some fresh-air diners.

"They left because of it," Brian Rebuck said of two coworkers who had reneged on a plan to share lunch on a bench in Washington Square. Only one remained with the Center City resident: Mayva Marshall of Society Hill.

It was their birthday, both of them, and they weren't retreating.

"We haven't been out here for quite a while," Rebuck said.

Could they stand snow?

"That," he conceded, "might keep us from coming out."