Look alive, astrology girlies and moonwater enthusiasts: a rare Blue Moon is about to rise, and let me tell you, it’s one hell of a celestial event! Read on for everything you need to know about this rare cosmic occurrence. What is a Blue Moon? Despite the name, the moon won’t actually turn blue (sorry to anyone expecting an Avatar-style sky situation). A Blue Moon is the term used when two full moons happen within the same calendar month, something that only rolls around every couple of years.