Halloween may be a little spookier this year. A blue moon is set to light up the sky on Oct. 31.
Many have heard the phrase, “once in a blue moon.” It refers to something rare, just like this celestial event. NASA says we’re only treated to blue moons every two and a half years, on average.
A blue moon is the second full moon in a calendar month, according to modern folklore. And since there are 29 days between moons and most months have 30 or 31 days, having two full moons in a month doesn’t happen often.
The next blue moon isn’t expected until Aug 31, 2023, according to MoonGiant.com.
Don’t expect a giant blue orb in the sky though. These moons look the same as any other.
Before the blue moon on Halloween, another full moon will appeared in the sky on Oct. 1. The first was called the harvest moon and the second will be referred to as the hunter’s moon, according to the Old Farmer’s Almanac.
The Farmer’s Almanac says a full moon on Halloween is also rare and only happens every 18 to 19 years.