Monday was hot, but most people took it in stride. After all, they said, this summer has been relatively cool — as far as Washington summers go.

Alex Sosnowski, an Accuweather meteorologist, attributed the comfortable weather of late to a “persistent” dip in the jet stream into the eastern United States. The dip, which remained until the last week in July, allowed one cool air mass after another to drain down out of Canada and then off the Atlantic seaboard.