Even after a hard Saturday night, some of us may have had a bit of trouble falling asleep in the small hours of Sunday, because of the bright light beaming into our bedroom windows.

It was the September moon, approaching its full stage, and about to confirm this as the summer of the four full moons.

That may sound puzzling, with summer’s lease lasting only about three months and almost a month needed for the moon to go through its phases.

But a four-full-moon summer such as this becomes possible if the first comes just after the June solstice, and the fourth just before the September equinox.

The moon’s early Sunday brilliance came because it was so close to being full. It will be full Monday, reaching peak brightness with about two days to spare before fall starts on Wednesday.

Thus the calendar crams in our fourth full moon this summer. The first came June 24, four days after the start of the season.

Of all the folkloric names borne by full moons, this may be the best known and most evocative. That bright beacon in south-facing windows is the Harvest Moon, so named for obvious agricultural reasons.

Meanwhile, Sunday showed we are headed for harvest season. Even in bright sunshine, thermometers rose no higher than 83.

With humidity mainly in check, many heads around the region seemed to nod in agreement that it was a fine day.