Friday The 13th's Harvest Moon Only Occurs Once Every 20 Years

This year's Harvest Moon is expected to be much smaller than the supermoon that rose over Half Dome in Yosemite National Park in November 2016. Phitha Tanpairoj/Shutterstock

This Friday, moon gazers in the Northern Hemisphere will be treated by a doubly special full moon as the Harvest Moon coincides with the notoriously superstitious Friday the 13th, an occurrence that only happens once in every 20 years, according to the Farmer’s Almanac.

The Harvest Moon marks the beginning of fall as the days get shorter and the air gets crisper. (At least for the northern half of the world. For those living in the Southern Hemisphere, the Harvest Moon generally occurs in March or early April.) This year’s autumnal equinox is on September 23, and a brightly lit Harvest Moon will allow harvesters ample time to work late into the night collecting the last of this year’s summertime crops. Some sources say the famous moon traces back to ancient Native American tradition, though modern records indicate Anglo-Saxons recorded its occurrence as early as the 8th century, according to

Like any other full moon, a number of factors characterize the Harvest Moon, particularly the time of moonrise. During most of the year, the moon rises around 50 minutes later each day. Near the equinox, the Harvest Moon rises closer to sunset, according to Those living in mid-temperate latitudes may even see the moonrise just 25 to 30 minutes later in the day – high northern altitudes, even less.

This year’s Harvest Moon is also a “micro-“ or “mini-moon” and will appear 14 percent smaller than other full moons in 2019. This is because the Moon will be at its greatest distance from the Earth.

“The Moon will be full early Saturday morning, September 14, 2019, appearing "opposite" the Sun (in Earth-based longitude) at 12:33 AM EDT. The Moon will appear full for about three days centered around this time, from Thursday night through Sunday morning,” according to NASA Science.

The agency notes that the brightest planet in the sky on September 14 will be Jupiter, “appearing in the south-southwest at about 24 degrees above the horizon.” Saturn will also appear in the south at around 29 degrees above the horizon.



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