Rare blue moon to light up the sky on Halloween
Mark your calendars for Oct. 31.
September 16, 2020, 5:14 PM
On Halloween, the sky will be lit up by a rare blue moon on the scariest night of the year!
![PHOTO: A full moon shines over an owl landing on the branches of a tree silhouetted against blue night sky in this undated photo.](https://s.abcnews.com/images/GMA/moonbranch-02-gty-iwb-200916_1600274775852_hpEmbed_3x2_992.jpg)
Arterra/Universal Images Group via Getty Images
While it is called a blue moon, the moon won't actually appear blue. The phrase refers to the time when a second full moon occurs in one month.
![PHOTO: The Full Corn Moon shines behind Hortiatis mountain over the city of Thessaloniki, Greece, Sept. 2, 2020.](https://s.abcnews.com/images/GMA/fullmoon-02-gty-iwb-200916_1600274775849_hpEmbed_3x2_992.jpg)
NurPhoto via Getty Images
According to NASA, a blue moon occurs about seven times every 19 years.
This year, there will be a full moon on Oct. 1 and on Oct. 31.
The last blue moon appeared March 31, 2018, according to Earth Sky.