Lately, blue moons haven't been as rare as their reputation suggests. The last one appeared at the tail-end of January and coincided with a super moon and a total lunar eclipse. The next blue moon is set to light up skies on March 31, and though it won't be accompanied by any of those celestial oddities this time, you shouldn't take it for granted: According to WZTV, this is your last chance to see one until 2020.
Unlike other events marking your meteorological calendar, blue moons aren't affected by anything going on in space so much as the date they happen to land on. A blue moon is the second full moon to occur within a single calendar month. The previous full moon fell on March 2, making it the last full moon of winter as well as a Full Worm Moon (that's an Old Farmer's Almanac term for a full moon that occurs when birds start searching for worms at the end of winter).
Although a blue moon is indistinguishable from a regular full moon, sky gazers have an additional reason to step outside on the night of March 31: Mercury will be close to Venus in the sky above the western horizon, making the solar system's smallest planet especially visible. The best time to spot it will be right after sunset, after which spectators can stick around to watch the full moon rise.
If you miss the blue moon this time around, you have more than two years to prepare for the next one. It's set to arrive on Halloween night 2020, so start planning your blue werewolf costume now.