It’s summer, but the daylight has started to wane; sunrise is later, sunset is earlier and you can notice it, too. (Photo by Greg Porter)

History tells us that summer’s heat may continue for many days, but on Friday, astronomy showed us that summer’s light has clearly started to fade.

In many ways, July 20, 21 and 22 represent the turning point of summer, possibly the occasion for a certain wistfulness and sense of loss.

We are now about a month past the summer solstice, and it has begun to show. Friday was the first day in July when the sun set in Washington before 8:30 p.m.

Saturday is the last day of the year on which the sun rises before 6 a.m. It also is Washington’s last day on which the seemingly boundless expanse of daylight — one of the great delights of the warm weather months — extends beyond 14 hours and 30 minutes.

Sunday happens to be the last day of the 16 day period in which, historically, Washington’s summer temperatures reach their peak of 89 degrees.

Nevertheless, summer heat typically lingers here well into August. For 19 of the 31 days of August, the record temperature has been 100 degrees or more.

And there is always humidity to help it seem hotter.