What Is a Harvest Moon?

Harvest Moon Facts and Folklore

By Fred Schaaf
September 7, 2018
Harvest Moon and Plane

In 2018, the Harvest Moon falls on September 24. But what is the Harvest Moon and why is it so special? Learn more—and shine on, Harvest Moon!

When is the Harvest Moon?

The Harvest Moon is the full Moon nearest the start of fall or the autumnal equinox. This usually means it coincides with the September full Moon, though it can also fall nearer to the October full Moon, occurring anywhere from two weeks before to two weeks after the equinox.

In 2018, the Harvest Moon will rise on Monday, September 24 at 10:52 P.M. (EDT).

Why is it Called the Harvest Moon?

For several evenings, the moonrise comes soon after sunset. This results in an  abundance of bright moonlight early in the evening, which was a traditional aide to farmers and crews harvesting their summer-grown crops. Hence, it’s called the “Harvest” Moon!

Hay bales

What Makes the Harvest Moon Different from Other Full Moons?

There are just a little over 12 complete Moon cycles every year, on average (there being about 29.53 days in a synodic month). The Harvest Moon isn’t like the other Moons. Usually, throughout the year, the Moon rises an average of about 50 minutes later each day. But near the autumnal equinox, the difference is only 30 minutes.

Additionally, the Full Harvest Moon rises at sunset and then will rise very near sunset for several nights in a row because the difference is at a yearly minimum. It may almost seem as if there are full Moons multiple nights in a row!

More Information About the Harvest Moon

If interested, here is more detailed information about the Harvest Moon. (Warning: Scientific explanation below!)  

The Moon’s orbital motion (combined with the larger orbit of the Earth around the Sun) carries it farther eastward among the constellations of the zodiac from night to night. At any one moonrise, the Moon occupies a particular place on the celestial sphere (the great dome of the heavens), but when the Earth turns toward that point 24 hours later, the Moon has moved off to the east about 12 degrees, and it takes an average of 50 minutes longer for the Earth to rotate toward the Moon and for the Moon thus to “rise.” Think of it as a giant Slinky in which each loop, representing one lunar orbit of the Earth, advances the orbit a bit farther along the spiral path.

But around the date of the Harvest Moon, the Moon rises about the same time. Why? Remember that the zodiac is the band of constellations through which the Moon travels from night to night. The section of the zodiac band in which the full Moon travels around the start of autumn is the section that forms the most shallow angle with the eastern horizon. Because the Moon’s orbit on successive nights is more nearly parallel to the horizon at that time, its relationship to the eastern horizon does not change appreciably, and the Earth does not have to turn as far to bring up the Moon.

The Moon may rise as little as 23 minutes later on several nights before and after the full Harvest Moon (at about 42 degrees north latitude), which means extra light at peak harvest time near autumn. By the time the Moon has reached last quarter, however, the typical 50-minute delay has returned.

At the start of spring, the opposite applies. The full Moon is in the section of the zodiac that has the steepest angle with respect to the eastern horizon. For several days bracketing the full Moon nearest the vernal equinox, the delay in moonrise is as much as 75 minutes (at 42 degrees north latitude).

Full moon and clouds

Here is another way of expressing what happens with the Harvest Moon: It is in this part of the zodiac that the Moon’s eastward (orbital) motion has its largest northward component. For observers in Earth’s Northern Hemisphere, the farther north an object is in the heavens, the longer an arc it makes across the sky, and the longer a time it is visible above the horizon. Thus, to say that the Moon is getting rapidly farther north each night around the time of the Harvest Moon is to say that, for northern latitudes on Earth, it will keep rising distinctly earlier than would otherwise be expected—nearly the same time as the night before.

How nearly the same is “almost the same time” each night? This varies with latitude, for the farther north you are, the shallower the angle of the zodiac is with respect to your horizon. In most of the United States and southern Canada, the Harvest Moon rises 25 to 30 minutes later each night. The effect is less noticeable the farther south you go. But going north makes the Harvest Moon more extreme.

According to astronomy author Guy Ottewell, the idea of the Harvest Moon originated in Europe (average latitude about 50 degrees north), where the Harvest Moon rises only ten to 20 minutes later each night. It must have seemed a boon that just when days were getting rapidly shorter and the Sun seemed to go down all too soon, the Harvest Moon arrived to extend the hours that harvesting could be done.

Low full moon

Chinese Harvest Moon Traditions

As a final note, I should add that it is not just Western civilization that has given special importance to the Harvest Moon. For Chinese people everywhere, this full Moon is the occasion for the Festival of the August Moon (the “August” is through a calendar discrepancy) or Mid-Autumn Festival (in some cultures, the equinoxes and solstices have been considered the middle of the seasons). This festival is celebrated with joyful games and the eating of “Mooncakes.”

I remember vividly being invited to one such celebration and singing songs and playing my guitar to a circle of friendly faces in the light of the rising Harvest Moon.

Learn More

Ever notice that the low-hanging Moon looks especially big near the horizon? It isn’t really significantly bigger. Learn more about this trick of the eye called the Moon Illusion.

Find out what your Moon phase is tonight and when the next full Moon is.

2020 Almanac Calendar Club

Reader Comments

Leave a Comment

2018 Harvest Moon

Won't be able to see it this year. Clouds and rain are in the forecast for most of this week. Temps and humidity are down, so there is that.

all informative

If I were to give a score between one and ten; you would get ten plus.

Slooh and the monthly Full Moon shows?

Does the Old Farmer's Almanac still partner with Slooh to do the full-moon streaming programs??? I haven't seen this in a while. I guess I can go directly to Slooh, but there were speakers on this video streaming show from the Old Farmer's Almanac, talking about both the scientific and the folkloric aspects of every month's full moon. What's the story, Old Farmer's Almanac? Do you still partner with Slooh???
Thanks in advance.

Slooh and the Almanac

Thank you for your enthusiasm for the SLOOH programs, Christine. We participated with the SLOOH folks for much of 2016, in the way that you describe—offering facts and lore about each month’s full Moon. In many shows, we had an editor, live-streaming from our offices, as well as our astronomer Bob Berman, live-streaming from his home or planetarium. The most recent show was in August, on the occasion of the Mini Strawberry Moon.

The partnership is still in place, but Almanac appearances/participation are as the producers/programmers need. We join in whenever we are asked. Thank YOU again for asking about it.

Harvest Moon

Very interesting, I'm ashamed to admit that I never really took an interest in such matters, it appears the older I have become, the more interest I have in such beautiful things, what's the saying, "youth is wasted on the young" funny !!!!

harvest moon article

Obviously only talking about the northern half of the Earth

Can you write this stuff so

Can you write this stuff so idiots like me can understand?

harvest moon

hi james, you are absolutely right, i wish i could understand it, it sounds very interesting. have a nice day, by the way, i am from austria

i like cakes - maybe

i like cakes - maybe mooncakes....otherwise very intersting all....!

well- even deeper, tis the

well- even deeper, tis the time of transition, the harvest as highest tide too, thus its sedna's birthday among the northern artic folk, she who has birth'd the sea, she who calls toward and from the underworld, this gate of change is celebrated too as a time to invoke mercy(catholic as our day that belongs to the honoring of Our Lady of Mercy), also as yom Kippur- day of atonement,the day in the pagan cosmology as the death and mourning of Demeter for Persephone, who descends to the underworld in contract with Hades, the great god of the dead, who wooed and wed her astride his black stallion, representing all the wildness which we cannot ever control, the changed to the dark of evil with our current entrance to the season of all hallows eve, halloween, but which otherwise is the day when the veil is thinnest to the other world, or under world! SO, this is a moon of great promise, great fate and fear and all hope. Happy harvest moon all!

Well said...Blessed Be.

Well said...Blessed Be.

Is there a Mooncake recipe?

Is there a Mooncake recipe?