Mark your calendars and set a reminder: a rare blue full moon will light up the night sky on Halloween. Make sure to take a look as a full moon will not occur on Halloween again until 2039!

As 2020 has already been an unique year, it is also a year with 13 full moons instead of the typical 12. In the month of October, there will be two full moons: the first on Oct. 1 and the second on Oct. 31. When two full moons occur in a single calendar month, the second is considered to be a blue moon. According to EarthSky, a blue moon tends to happen around every 2 to 2 ½ years. The moon, however, will not appear blue in color.

This month’s blue moon occurs on Halloween and a full moon on this day is rare. The last time that a full moon was visible on Halloween in all time zones was in 1944, according to the Farmer’s Almanac. A Halloween full moon occurs in some time zones roughly every 19 years due to the Metonic Cycle. Based on this, we will not see a full moon on Halloween again until 2039, 2058, 2077 and so on.

The full moons of each month are given specific names, dating back to Native American folklore. The full moon on Oct. 1 was the Harvest Moon. According to NASA, the full moon closest to the autumn equinox is called the Harvest Moon because farmers would use the light of the moon to work into the night during harvest season. The next full moon to follow the Harvest Moon is called the Hunter’s Moon as hunters used its moonlight to hunt and prepare for winter. This allows the moon on Halloween to earn the special title of the Hunter’s Blue Moon.

The Hunter’s Blue Moon will reach its peak illumination at 10:51 a.m. on Halloween morning but will still appear full that night, according to the Farmer’s Almanac. The moon this Halloween is not one to miss!