It was unusually warm in the Washington area Sunday, warm enough to set a record at one of the area’s airports and warmer than it might get for the rest of the year.

Temperatures at all three of the area’s airports reached into the 70s, and at Dulles International Airport, the maximum of 70 was a record. The old record at Dulles was 68, set in 1976.

At Reagan National Airport, where Washington’s official readings are made, it was even warmer, 72 degrees. That made for an enjoyable afternoon for many, but it fell three degrees short of the record of 75, set 115 years ago.

“Feels like mid-April” said a post on the Washington Post’s Capital Weather Gang site. “Amazing weather!” exclaimed another.

Travelers returning to the area after the Thanksgiving weekend found it much warmer than in Chicago, where Sunday’s high was 46, or Cleveland, where the high was 59, or New York, where the Central Park high was 63.

It was just a little cooler in Washington than Atlanta’s 73, or at Raleigh-Durham airport in North Carolina, where 75 was measured.

According to a National Weather Service analysis of Washington weather data, 2011 has about a 50-50 chance of ending without another day quite so warm or atmospherically amazing as Sunday.

An examination of Washington records going back to 1872 shows that in all the years since then, temperatures from Nov. 28 to Dec. 31 have reached 70 only 70 times, the weather service said.

That means, the service said, that a 70-degree day from now to year’s end occurs, on average, about once every two years, which suggests that residents and visitors who rejoiced in Sunday’s balmy sunshine and shirt-sleeve conditions may not see anything quite like it again in the last 34 days of this year.

In a Sunday forecast, The Post’s weather gang anticipated that the highs Monday would reach the 60s. The weather service also called for 60s. But it said that more sunshine would make possible another 70-degree day.

Sunday was Washington’s second-warmest day this month at National, one degree short of the high of 73 reached Nov. 14.