Friday, September 13th 2019, 11:53 am - We won't see another of its kind for over 150 years!
When the Full Moon rises this Friday night, it will be the one of the rarest Harvest Moons ever!
The last time we saw a Friday the 13th Harvest Moon was in 1935 (technically), as the Full Moon rose on the night of Thursday, September 12 and set in the morning on Friday, September 13.
To have a Harvest Moon like we're seeing this Friday, however, with the Full Moon rising on September 13 and setting on September 14, you have to go back 152 years, to the year 1867!
The next time we'll see a Friday the 13th Full Moon will be in August of 2049, but for a Friday the 13th Harvest Moon, we'll have to wait much, much longer... until September of 2171!
Diane Kawaza posted this image of the October 2017 Harvest Moon to the Weather Network photo gallery
Now, technically the Full Moon doesn't happen until exactly 4:35 UTC on September 14, or 12:35 a.m. EDT on Saturday, however since the Moon is considered to be a Full Moon all night, it still counts!
WILL YOU SEE IT?
Weather Network meteorologist Tyler Hamilton has the scoop on who will have the best chance to see this rare Harvest Moon, based on the sky conditions.
WHAT IS A HARVEST MOON?
We have many names for the dozen or so Full Moons we see each year. Most of them are specifically related to one particular Full Moon in the order - Wolf Moon, Snow Moon, Worm Moon, etc. There's one name that doesn't always apply to the same Full Moon each year, though. This is the Harvest Moon.
A Harvest Moon is the Full Moon that falls closest to - either before or after - the Autumnal Equinox. Thus, it is always the Full Moon in either in mid-to-late September, or early October that is chosen as the Harvest Moon.
For 2019, the September 13-14 Full Moon is this year's Harvest Moon because it occurs just 10 days before the Equinox, whereas the October 13-14 Full Moon is 20 days after.
Chris Knox posted this view of the October 2017 Harvest Moon, as seen from Brighton, Ontario
WHY IS THIS HARVEST MOON SO RARE?
It has been 152 years since the last time we saw a Harvest Moon like Friday's, and it will be another 152 years before we see a Friday the 13th Harvest Moon again. Why, though, is a Friday the 13th Harvest Moon so rare?
For a Friday the 13th Full Moon to also be the year's Harvest Moon, it must fall on September 13.
Why, you may ask? Full Moons happen every 29 days or so, give or take a few hours. Thus, a Friday, October 13 Full Moon - around 20 days after the Equinox - would be preceded by a September 13 or 14 Full Moon - around 10 days before the Equinox. Thus, the September Full Moon is closer to the Equinox, and therefore would be the Harvest Moon.
So, the rarity of this Full Moon comes down to lining up the timing of two very specific events - having a Full Moon rise on one specific day of the year, and having that one specific day of the year fall on a Friday.
From the years 1867 to 2095, there's exactly 19 years between occurrences of having a Full Moon fall on September 13-14. It's like clockwork! There's a few skips and jumps after that, based on the exact time of the day when the Moon becomes full, so we see them happen again in 2106, in 2152, and then in 2171.
For that same timespan, having September 13 fall on a Friday occurs every 5 or 6 years, also with a few skips and jumps which mostly depend on the timing of when leap years happen.
With neither of these schedules working with consistent, round numbers, you can see how it gets tough for them to line up. Add in the skips and jumps both schedules make from time to time (especially with Full Moons in the 2100s!), and putting these two events on the same day gets even tougher!
Note: Harvest Moon teaser image captured by Jeff Taylor, on October 5, 2017, and uploaded to The Weather Network UGC gallery.