Why 2025's Harvest Moon is a rare October full moon

Our next full moon will occur on Oct. 6, and it will be a somewhat special one for those living in the Northern Hemisphere in that it will also carry the title of "Harvest Moon." The moon officially turns full when it reaches that spot in the sky opposite (180 degrees) to the sun in the sky and this moment will occur on Tuesday, Oct. 7 at 03:48 GMT (which corresponds to 11:48 p.m. EDT on Oct.6, or 8:48 p.m. PDT).

But it also turns out that this full moon is the one that comes closest on the calendar to the September equinox. In 2025, this circumstance comes later than usual, into the month of October, as opposed to the more traditional month of September. Full moon in September came on Sept. 7 and occurred 15.006 days prior to the autumnal equinox. The full moon of Oct. 6 occurs 14.395 days after the equinox, or 14 hours and 39 minutes nearer to the equinox than September's full moon.

Thus, the 2025 version of the Harvest Moon falls in October, although, for U.S. time zones, it can occur as early as Sept. 8 (as in 2014) or as late as Oct. 7 (as in 1987).

October oddities

Between 1970 and 2050, there are 18 years when the Harvest Moon comes in October. The last time was in 2020 and the next time will be in 2028. On average, October Harvest Full Moons come at three-year intervals, although the time frame can be quite variable and there can be situations where as much as eight years can elapse (the next such example will come between 2028 and 2036).

Harvesting by the light of the moon

Full Moon names date back to Native Americans of what is now the northern and eastern United States. Those tribes of a few hundred years ago kept track of the seasons by giving distinctive names to each recurring full moon. Their names were applied to the entire month in which each occurred. At the peak of the harvest, farmers can work into the night by the light of the Harvest Moon. Corn, pumpkins, squash, beans, and wild rice — the chief Indian staples — are now ready for gathering.

Not a "long night's moon"

It seems that most people are under the impression that the Harvest Moon remains in the night sky longer than any of the other full moons we see during the year, but that's not so. It's the full moon occurring nearest to the winter solstice that stays above the horizon the longest, at mid-northern latitudes in excess of 15 hours. What sets the Harvest Full Moon apart from the others is that it rises about the time the sun sets, but more importantly, at this time of year, instead of rising its normal average 50 minutes later each evening, the moon seems to rise at nearly the same time each night. In fact, this unusual circumstance, a full (or nearly full) moon appearing on several consecutive evenings near sunset, rising at roughly the same time each night and leaving only a short period of darkness, was once considered a special provision of nature to allow farmers to continue working into the night without interruption.

For example, in Boston, Massachusetts, moonrise on Oct. 5 is at 5:32 p.m. On Oct. 6, moonrise is 5:55 p.m. and on Oct. 7, it's 6:20 p.m. So compared to the normal 50 minutes per night, around the time of the Harvest Moon, the moonrise comes about 24 minutes later.

Worldwide variations

In actuality, the night-to-night difference is greatest for more southerly locations. For example, Miami, Florida, located near latitude 25.8 degrees N, sees moonrise come an average of 37 minutes later. Meanwhile, the difference is less at more northerly locations; at Edmonton, Alberta, Canada, located at a latitude of 56.7 degrees N, the average difference is only 11 minutes. The reason for this seasonal circumstance is that the moon appears to move along the ecliptic and at this time of year, when rising, the ecliptic makes its smallest angle with respect to the horizon for those living in the Northern Hemisphere. In contrast, for those living in the Southern Hemisphere, the ecliptic at this time of year appears to stand almost perpendicular (at nearly a right angle) to the eastern horizon. As such, the difference in the time of moonrise exceeds the average of 50 minutes per night. At Christchurch, New Zealand (43.5 degrees S), for instance, the night-to-night difference amounts to 81 minutes.

Interestingly, for those who live near 70 degrees north latitude, the moon does indeed appear to rise at the same time each night around the time of the Harvest Moon. And for those who live even farther to the north, a paradox: the moon appears to rise earlier! At Barrow, Alaska (latitude 71.3 degrees N), for instance, the times of moonrise on Oct. 5, Oct. 6 and Oct. 7 will be, respectively, 7:16 p.m., 6:39 p.m. and 5:51 p.m.

So, from Barrow, the moon will seem to rise about 43 minutes earlier each night!

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope and other publications.