There will be two full moons in October 2020 – the first one will appear on October 1 or 2, 2020. It depends on which part of the world you live in. This full moon is called Harvest Moon in the Northern Hemisphere and counts as autumn’s first full moon. Moreover, it is spring’s first full for the Southern Hemisphere. Regardless of where you live, expect a full-looking moon to brighten up the sky from dusk till dawn within the next few nights. Furthermore, that bright red “star” close to the moon is not a star at all. It is the red planet – Mars.
A season is described as the time span between the equinox and the solstice, or vice versa. Usually, one season has 3 full moons, and in 2020 the season between the fall 2020 equinox and the winter 2020 solstice brings the usual three full moons.
- September 2020 equinox: September 22 at 13:31 UTC
- Full moon: October 1 at 21:05 UTC (Harvest Moon)
- Full moon: October 31 at 14:49 UTC (monthly Blue Moon)
- Full moon: November 30 at 9:30 UTC
- December 2020 solstice: December 21 at 10:02 UTC
Since this October will have two full moons, some people will name the second one the Blue Moon. It falls on October 31.
The full moons in 2021 will occur about 11 days earlier compared to this year. Unsurprisingly, the full moon in September next year will occur on September 20, 2021. That is 11 days before October 1. Besides, this will be the full Harvest Moon for the Northern Hemisphere, but the last for the summer season. In addition, there will be four full moons (instead of the usual three full moons between the June 2021 solstice and the September 2021 equinox.
- June 2021 solstice: June 21 at 3:32 UTC
- Full moon: June 24 at 18:40 UTC
- Full moon: July 24 at 2:37 UTC
- Full moon: August 22 at 12:02 UTC (seasonal Blue Moon)
- Full moon: September 20 at 23:55 UTC (Harvest Moon)
- September 2021 equinox: September 22 at 19:21 UTC
It’s a bit unusual to see four full moons in one season, and some people use the term Blue Moon for the third of four full moons in a season. Almanac writers decided to name the third full moon (instead of the fourth one) of the season the Blue Moon. Therefore, the full moon terminology fits the other three full moons of the season.
Full moons in the near future
Usually, a calendar year having a monthly Blue Moon (second of two full moons in 1 month) follows up a calendar year with a seasonal Blue Moon (third of four full moons in one season). Moving forward to the year 2023, the monthly Blue Moon on August 31, 2023, will be preceded by the annual full moon on August 19, 2024; and moving forward to the year 2026, the monthly Blue Moon on May 31, 2026, will be preceded by the seasonal Blue Moon on May 20, 2027.
Meanwhile, the Harvest Moon in the Northern Hemisphere is always the full moon that appears the closest to the autumn equinox; no matter if it is the last full moon of summer or the first full moon of autumn. The Harvest Moon this year will be full on 1 October 2020 at 21:05 UTC. While the moon is full at the same time around the planet, the clock time of the full moon depends on the time zone. At the North American and U.S. time zones, this puts the full moon instant around our daylight hours (when the moon is still under our horizon) on October 1 at 6:05 p.m. ADT, 5:05 p.m. EDT, 4:05 p.m. CDT, 3:05 p.m. MDT, 2:05 p.m. PDT, 1:05 p.m. Alaskan Time and 11:05 a.m. Hawaiian Time.
Each full Harvest Moon appears to rise in the east during sunset and set in the west around sunrise.
In the nights after the full Harvest Moon of the Northern Hemisphere, the fading gibbous moon rises even further north along the eastern horizon every day for almost a week. On the Northern Hemisphere, these more northerly moonrises decrease the lag period between consecutive moonrises to a minimum per year (and in the Southern Hemisphere, these more northerly moonrises increase the lag period to a maximum per year).
While the impact is small in the tropics, the occurrence of the Harvest Moon is more intense in high latitudes.
On average, the moon rises about 50 minutes later daily. But at 40 degrees north latitude, the moon is only rising about 25 minutes later a day (instead of 50 minutes). And at about 60 degrees north latitude, the moonrise arrives at or about the same time for almost a week.
- Denver, Colorado (40 degrees north latitude)
- Moonrise September 30: 6:40 p.m. MDT (Mountain Daylight Time)
- Moonrise October 1: 7:03 p.m. MDT
- Moonrise October 2: 7:27 p.m. MDT
- Moonrise October 3: 7:51 p.m. MDT
- Source: Old Farmer’s Almanac
The Harvest Moon occurs because the ecliptic – average monthly course of the moon – intersects the horizon at its shallowest angle of the year at sunset at the autumn equinox. In the equator and the tropical regions of the planet, though, the ecliptic always intersects the horizon at a steep angle, so that the impact of the Harvest Moon is minimal. However, at and close to the Arctic Circle, the ecliptic is more or less parallel to the sundown horizon at this time of year, indicating that the moon is rising almost to the same time for days on end. In far-northern latitudes, it is often common for the moon to rise earlier day by day.
- Fairbanks, Alaska (65 degrees north latitude)
- Moonrise September 30: 7:57 p.m. AKDT (Alaska Daylight Time)
- Moonrise October 1: 7:54 p.m. AKDT
- Moonrise October 2: 7:51 p.m. AKDT
- Moonrise October 3: 7:49 p.m. AKDT
- Source: Old Farmer’s Almanac
In the years before electricity, farmers in the northern latitudes were counting on the Harvest Moon lamp to collect their crops. The Harvest Moon is faithfully offering a few nights of dusk-till-dawn moonlight to make up for the fall season’s fading sun. This bonanza of moonlit nights is still the legacy of the Harvest Moon!