In January, we promised our readers that 2020 would be a stargazer’s treat, especially when it came to full Moons. In total, for 2020, we’ll have 13 full Moons, including 2 two Supermoons, and a full Moon on Halloween, which is more uncommon than you may realize. Read on to learn more!

13 Full Moons in 2020

The first full Moon of 2020 howled onto the scene with January’s Wolf Moon on January 10th. And usually, we have one for each month, making the total 12 for the year. But on occasion, some months will have two full Moons. This is the case for October 2020: we’ll have a full Moon on Thursday, October 1st, which will be the Harvest Moon, and again on Saturday, October 31st—a Halloween full Hunter’s Moon in all time zones (the Moon turns full at 10:49 a.m. EDT), making this a super fun rare treat.

See all the dates and times of the year’s full Moons.

Rare Halloween Blue Hunter’s Moon in 2020

When we think of “All Hallow’s Eve,” many of us conjure up terrifying images of werewolves, goblins, zombies, and other scary things that go “bump” in the night, all lit up by a spooky full Moon. But how common is a Halloween full Moon? Apparently, not very.

In 2001, ghosts and goblins in Central and Pacific time zones trick-or-treated by the light of a full Moon, but a Halloween full Moon hadn’t appeared for everyone in all time zones since 1944!

When you look at the full Moon on Halloween night, it won’t appear blue in color but you’ll be looking at something pretty uncommon. A full Moon on Halloween occurs roughly once every 19 years—a pattern known as the Metonic Cycle. 

This well-known lunar cycle was discovered in 432 BC by the Greek, Meton, of Athens. He determined that after 19 years have elapsed, the phase of the Moon will repeat on the same date. Well , not always. Because of slight variations in the Moon’s orbital period, and the number of leap days that intervene over a 19-year time span, the Metonic Cycle can be accurate only to within a day.

For a Halloween full Moon, the Metonic Cycle worked well early in the 20th Century—in the years 1925 and 1944.  But thereafter, using the cycle, the date of full Moon shifted a day to November 1st (in 1963, 1982, and 2001). But then, in 2020, it returned to October 31st. Making it a rarer sight, indeed.

But for 2020 on through the balance of the 21st century, a full Moon on Halloween will occur once every 19 years.

Blue Moon Definition

For more than half a century, whenever two full Moons appear in a single month (which happens on average every 2 1/2 to 3 years), the second full Moon is christened a “Blue Moon.”

Fun fact: Any time the Moon is technically “full” on October 31st (as it will be this year), it would also have to be a Blue Moon because the lunar cycle is only 29.5 days long.

There is an alternate definition of a “Blue Moon”—when there are 4 full Moons in a single season, the third is considered a “Blue Moon.” 

When’s The Next Halloween Full Moon?

According to astronomers, we will all see a 100%-illuminated Halloween full Moon (after 2020) in the years  2039, 2058, 2077, and 2096 (note the 19-year pattern). The good news is that even if the Moon is a day or two away from 100% full on any particular Halloween, it can still serve the purpose for a spooky backdrop since most people can’t tell the difference between a 98% illuminated Moon and a 100% “full” Moon (Cases in point: November 2, 2029, and October 30, 2031). Plan your costumes accordingly!

October’s Full Moon Dates and Times

October 1st – The full Harvest Moon, at 5:05 PM EDT

October 31st – The full Halloween Hunter’s Blue Moon (quite a mouthful!), at 10:49 AM EDT

We Had 2 Supermoons in 2020

For a Supermoon to occur, we can thank the shape of the Moon’s orbit, which is not a perfect circle, but an oval shape. That means when the Moon orbits the Earth each month, it reaches a point that’s farthest from the Earth, called apogee, and a point where it swings closest to Earth, called perigee.

According to how most people define a Supermoon, it occurs when the Moon is at least 90% of the way to its perigee position at the same time it is in its “full” phase.

Based on this definition, we experienced two Supermoons this year:

  • March’s Worm Moon turned 100% full on March 9th—Moon at perigee on March 10thApril’s Pink Moon turned 100% full on April 7th —Moon at perigee on April 7th

When we have a Supermoon, the Moon can appear as much as 14% larger and 30% brighter than a normal full Moon.

With all this special full Moon activity in 2020, be sure to mark your calendars so you don’t miss a thing!