Science Space 11 Things to Know About This Year’s Harvest Moon This year’s Harvest Moon rises in all its gorgeous glory on October 1. By Melissa Breyer Editorial Director Hunter College F.I.T., State University of New York Cornell University Melissa Breyer is Treehugger’s editorial director. She is a sustainability expert and author whose work has been published by the New York Times and National Geographic, among others. our editorial process Melissa Breyer Updated September 30, 2020 Ambre Haller / Getty Images Share Twitter Pinterest Email Science Space Natural Science Technology Agriculture Energy Each year as summer in the Northern Hemisphere slowly slips into autumn, we have the September and October full moons to shine their luminous light on the change of seasons. When the September full moon occurs closer to the autumnal equinox it’s called the Harvest Moon. But if the October full moon is closer to the date, she takes the title. This year, the October full moon is the Harvest Moon. All full moons are special, but the Harvest Moon has some unique features that make it a marvelous must-see. 1. 2020's Harvest Moon will be officially full at 5:05 p.m. Eastern Daylight Time on October 1 – this is when it is directly opposite of the sun. But it will appear full for a day or two before and after as it waxes and wanes. 2. Between 1970 and 2050, the October full moon will only claim the Harvest Moon title in 18 of those years. The last time was in 2017. October Harvest Moons come every three years on average, although as many as eight years can elapse between them. 3. Harvest moons can happen as early as September 8 or as late as October 7, making this year’s relatively late. 4. Sometimes the full moon happens on the equinox itself, the Harvest Moon last perfectly coincided with the autumnal equinox in 2010, and will do so again in 2029. 5. According to early Native American tradition, the calendar was marked by cycles of the moon, and thus, each one has a seasonal significance and name. The October moon has been variously known as the Full Hunter's Moon, the Travel Moon, and the Dying Moon. The Harvest Moon by George Hemming Mason (1871). Wikimedia Commons 6. The autumnal equinox full moon is called the Harvest Moon because its unique features traditionally helped farmers. The term dates back to at least the 18th century, according to the OED. 7. During the rest of the year, the moon rises up to a full 73 minutes later each successive day of its cycle. But the Harvest Moon rises in as little as 23 minutes later each day. As it turns out, during this time of year the moon’s orbit is more nearly parallel to the horizon and thus its relationship to the eastern horizon does not change much from day to day. 8. While all full moons rise at sunset, the fact that the Harvest Moon has a shorter rising lag on successive days means that we get what appears to be a full moon rising near sunset for more days than usual; this gave farmers a “sunset extension” of sorts, which went to good use during the very busy time of harvest. 9. The sunset-moonrise concurrence also simply makes for a spectacular spectacle, which we are treated to for several days. Low-hanging moons at sunset are reddened by clouds and dust, giving them that surreal “giant floating pumpkin” effect that so perfectly ushers in the fall. 10. And about the giant part; the Harvest Moon is like the moon poster child for the so-called “moon illusion,” in which a horizon-hovering moon appears to be gigantic. The moon actually doesn’t change size, it’s just a trick of the eye – one theory suggests that in relation to terrestrial objects the moon appears much larger than when it's floating in the vast heavens. Though, it's a bit more complicated than that, as you can see in the video below. 11. That said, this year's Harvest Moon is also a micro full moon, meaning it will appear slightly smaller and less bright in the sky than a regular full moon. But to make up for it all, the moon will be rising in tandem with the brilliant red planet, Mars in a show that sky-gazers won't want to miss.