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Harvest Moon on Friday the 13th

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September 12, 2019

On September 12, 13 and 14, 2019, look for a full-looking moon to light up the nighttime sky from dusk until dawn. Depending on where you live worldwide (your time zone), this month’s full moon will fall on Friday, September 13, or Saturday, September 14. For the Northern Hemisphere, this September full moon counts as the closest full moon to the September autumn equinox, so it’s the Northern Hemisphere’s full Harvest Moon. For many, it’ll be a Friday the 13th Harvest Moon … great party theme!

The last time that the Northern Hemisphere’s full Harvest Moon fell on a Friday the 13th (for at least a portion of the world) was in the year 1935, and the next time won’t be until the year 2171.

Read more: Two Friday the 13ths in 2019

In the Southern Hemisphere, the September equinox ushers in the spring season. The Southern Hemisphere’s autumn equinox will come six months from now, on March 20, 2020. And the full moon on March 9, 2020, will be the Southern Hemisphere’s Harvest Moon – the full moon closest to their autumn equinox.

What is a Harvest Moon? It’s more than just a name. More about the Harvest Moon phenomeon below.

This full moon is also the smallest full moon of 2019. More about the mini-moon or micro-moon below.

Want more about full moons and Friday the 13ths? Look below for that, too.

Large orange moon rising behind a mountain ridge with owl on tree in foreground. — 2018’s Harvest Moon rising on September 24 from Heidi Gabbert of San Jose, California.

But first, let’s think about what makes a full moon. Although the moon appears full to the eye for a few to several days in succession, it’s only truly full for a fleeting instant. Astronomically speaking, the moon is full at the moment that it’s exactly 180 degrees opposite the sun in ecliptic longitude.

This month, that moment falls on September 14 at 04:33 Universal Time. The full moon occurs at the same instant worldwide, but the local clock time varies by time zone. At time zones in the United States, the full moon falls on Saturday, September 14, at 12:33 a.m. EDT. But it falls on Friday, September 13, at all other U.S. times (11:33 p.m. CDT, 10:33 p.m. MDT and 9:33 p.m. PDT).

Visit Sunrise Sunset Calendars to find out when the moon turns full in your time zone, remembering to check the Moon phases box.

Diagram: Celestial sphere with slanted circle of ecliptic at a low angle to the horzon. — In early autumn, at sunset, the angle of the ecliptic – the sun’s yearly path or the moon’s monthly path in front of the constellations of the zodiac – makes a narrow angle with the horizon. Image via classicalastronomy.com.

What is a Harvest Moon? The term Harvest Moon might be of European origin. Many moon names are just names … but the Harvest Moon phenomenon is something else, a real physical phenomenon that you can notice.

Sailboat on Lake Ontario with large pale pink Harvest Moon in lavender sky. — View larger at EarthSky Community Photos. | What better place to watch the moonrise than from a sailboat? Steven Sweet of Mississauga, Ontario, Canada, caught the rising moon low in the eastern sky on September 12, 2019, at 7:27 p.m. EDT. Thank you Steven!

All full moons rise at or around sunset and are highest in the sky at or around midnight. But after this September full moon, from both the Northern and Southern Hemispheres, you’ll find the moon rising farther and farther north along the eastern horizon each day for about a week. Don’t know which way is north? No problem. As you stand facing eastward, north is to your left.

On the average, the moon rises 50 minutes later each day. For us in the Northern Hemisphere, however, these northbound moonrises following the September full moon reduce the lag time between successive moonrises to a yearly minimum. (In the Southern Hemisphere, where the September equinox is the spring equinox, these northbound moonrises following the September full moon increase the lag time between successive moonrises.) So around the autumn equinox – from the Northern Hemisphere in September or October, or the Southern Hemisphere in March or April – a full or nearly full moon rises closer to the time of sunset, on successive evenings, for several evenings in a row.

Check out the chart below.

Horizon with the slanted path of the moon. — The narrow angle of the ecliptic means the moon rises noticeably farther north on the horizon from one night to the next. So, as viewed from northerly latitudes, there’s no long period of darkness between sunset and moonrise. Image via classicalastronomy.com.

From 40 degrees north (Denver, Colorado; Philadelphia, Pennsylvania; Beijing, China), the moon now rises some 25 (instead of 50) minutes later daily. From Anchorage, Alaska (just north of 60 degrees north latitude), the moon rises about eight minutes later daily.

The higher the latitude, the greater the Harvest Moon effect – the effect of no great lag time between sunset and moonrise – in the season of waning daylight.

Before the advent of artificial lighting, people planned nocturnal activity around the moon, knowing the moon provides dusk-till-dawn moonlight on the night of the full moon. Hence the name Harvest Moon.

So the Harvest Moon phenomenon – a full or nearly full moon rising close to the time of sunset for several successive evenings – happens in September and October for our hemisphere, and March and April for the Southern Hemisphere. There is no Harvest Moon at the equator and not enough of one to say so in the tropical regions of the globe. You really have to be well north (or south) of the tropics to observe the year’s grandest parade of moonlit nights around the time of the autumn equinox.

This bonanza of moonlight in the season of waning daylight remains the legacy of the Harvest Moon.

Short pier into pond with red shed on the end in a brightly moonlit landscape. — Full Harvest Moon over a cranberry bog — in Wareham, Massachusetts, September 24, 2018 – by Jacob Baker.

Smallest full moon of 2019. By the way, this full moon is also being called a micro-moon or mini-moon because it’s the farthest (and therefore the smallest) full moon of the year. This full moon comes one fortnight (approximately two weeks) after the new moon supermoon on August 30, 2019, and one fortnight before the new moon supermoon of September 28, 2019.

Four years ago, the Harvest Moon of September 28, 2015, presented the closest (and therefore the largest) full moon of 2015.

The September 2019 full moon is the nearest full moon to the September equinox; yet, at the same time, it’s the farthest full moon of the year.

Full moons and Friday the 13ths. By Universal Time, the last time the full moon fell on Friday the 13th was on June 13, 2014, and the next time will have to wait until August 13, 2049. In the 21st century (2001 to 2100), a full moon falls on Friday the 13th for a total of eight times (by Universal Time).

Dim photo of huge wide waterfall and glowing yellow full moon above. — Harvest moon rising over Niagara Falls – September 24, 2018 – between the Canadian province of Ontario and the American state of New York, by Bonnie Halda.

Bottom line: The Harvest Moon – closest full moon to the September equinox – falls on Friday, September 13, in 2019.

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September 12, 2019

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Bruce McClure

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About the Author:

Bruce McClure served as lead writer for EarthSky's popular Tonight pages from 2004 to 2021, when he opted for a much-deserved retirement. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also wrote and hosted public astronomy programs and planetarium programs in and around his home in upstate New York.