JACKSONVILLE, Fla. — What is the Harvest Moon? It might seem like a straight forward answer, it's just a full moon in autumn right? Or maybe a full moon in September or October. Both answers would be correct.
The Full Harvest Moon is the moon that falls the closest to the Autumn Equinox. This year, in 2021, that is Sept. 22. Since there is a full moon on Sept. 20, that is given the name "Harvest Moon."
This is unique because most of the other names for full moons are based on what ever month they fall in. For example, that traditional moon name for October is the "Hunter's Moon."
The Harvest Moon is unique though, as it rises right near sunrise, allowing for near continuous light from the sun then the full moon. Fantastic for people prior to the invention of artificial lighting.
Furthermore, the moon peaks on Monday, Sept. 20 but due to the nature of the Harvest Moon it will be 98% full Monday, 100% full Tuesday and 98% full on Wednesday.
This will lead to several days of pretty much a full moon.
Thus, once again, before the invention of artificial lightning it was very useful and something farmers would plan around. Because of this, it gets the name the Harvest Moon.