A harvest moon occurs once every year, specifically it is the full moon closest to the autumnal equinox, which is around September 22 or 23. This means it typically happens once a year, near the start of fall in the Northern Hemisphere. Occasionally, around every three years or so, the harvest moon can occur in October instead of September due to the calendar alignment. The defining characteristic of the harvest moon is that the moon rises at nearly the same time on several nights in a row around this period, giving extra evening light useful during the traditional harvest season.
