The closest full moon to the autumnal equinox — typically known as a “harvest moon” — is slated to rise on or shortly after Friday the 13th, depending on the time zone, in a rare moment on the lunar calendar in the northern hemisphere.
The moon should appear full from Sept. 12 until Sept. 15, although NASA says it won’t be completely full until 9:30 pm. PST on Sept. 13 (or 12:30 EST on Sept. 14).
The name “harvest moon” is an old European term applied to a full moon that rises closest to the beginning of fall, NASA says. The bright light of the moon allows farmers to work a little bit later into the night to bring in their crops before fall sets in.
Skywatchers have a name for every full moon in a month, but the harvest moon is more than just a name. While most moons rise approximately 50 minutes after sunset, the harvest moon can appear as soon as 10 minutes after the sun sets.
In Toronto, for example, the sun is slated to set at 7:31 p.m., and the moon is expected to rise at 7:46 p.m. on Friday, according to the website Time and Date. The gap is even shorter in more northern latitudes.
The first day of fall will arrive on Sept. 22 or 23, depending on the time zone.
The next harvest moon on a Friday the 13th won’t come until August 2049.