Weather, like history, has its turning points, and the moment when Washington swung toward summer may have occurred Monday at 1:39 p.m. According to a preliminary report, that was when the mercury at Reagan National Airport reached 80 degrees.

Summer in Washington means the 90s. But before that characteristic swelter settles in, meteorology and mathematics require that some time be spent in the 80s.

It appeared that the 80-degree milestone was reached Monday at both National and Dulles International airports, for the first time since Oct. 24.

At Dulles, the reading of 80 meant a four-day, 58-degree climb from Thursday’s low of 22.

Responses to Monday’s conditions showed up all over. In a single minute amid the homebound 5 p.m. crowds at 17th and H streets NW, one woman stripped off her sweater and another remarked to her companion, “. . . and it’s going to stay warm.”

Forecasts suggest that it will do that, at least for a little while, reaching the 80s on Tuesday, Wednesday and Thursday.