Blue moons happen, well, once in a blue moon. And tonight, we’ll have a blue moon.
Blue moon is the name given to the second full moon in a month, an occurrence that happens on average every 2.7 years.
There was a full moon on Aug. 2 and another one tonight (Aug. 31), making this one “blue.”
Don’t expect the moon to actually appear to be the color blue, unless you’re looking at it through a telescope with a blue filter.
You don’t need to hire Maddie and Dave of the Blue Moon Detective Agency from TV’s Moonlighting to figure out why tonight is a full moon. The reason is simple. It takes the moon 29.5 days to orbit the earth, but each calendar month has 30 or 31 days (except for February).
Maddie and Dave might, however, tell you that the two-full-moons-in-a-single-month definition is the modern, more recent one. In older times, farmers defined it as the third full moon in a season (spring, summer, fall or winter) that has four full moons rather than the standard three to a season.
Anyone looking for good luck (or bad luck) tonight will likely be out of luck. There are no superstitious connections to blue moons. It’s just a rare or unusual occurrence, hence the phrase “once in a blue moon.”