Experience a “once-in-a-blue-moon” phenomenon tonight

When a season has four full moons – the third one is a blue moon – but not necessarily blue

A July blue moon will grace the skies on Friday in a phenomenon that occurs only once ever few years. This doesn’t mean that there will be blue light. A blue moon is just the second full moon in a calendar month or the third full moon of four every season.

The rarity of the blue moon phenomenon is how the phrase “once in a blue moon” came to be.