Traditionally, this designation goes to the full moon closest to the autumnal equinox. In two years out of three, the harvest moon appears in September, but every third year it occurs in October.

At this time of year, corn, pumpkins, squash, beans, and wild rice—the chief Native American staples—are ready for gathering; and at the peak of the harvest, farmers could work into the night by the light of this full moon.

Most of the year, the moon rises an average of 50 minutes later each night, but for the few nights around the harvest moon, the moon seems to rise at nearly the same time each night: just 25 to 30 minutes later across the United States, and only 10 to 20 minutes later for much of Canada and Europe.

A special name was reserved for those years that the harvest moon comes very late in September or early in October. In such situations, the full moon occurring immediately prior to the harvest moon (in late August or early September) was called the fruit moon or the barley moon.