If you look to the skies this Halloween you’ll see a rare Blue Moon. The full moon won’t actually look blue, but is called a Blue Moon because it is the second full moon to appear in the same month—the first appeared on October 1st. This phenomenon takes place seven times every 19 years, so the next time there will be a Blue Moon on Halloween will be the year 2039.
EarthSky reports this special full moon will be visible all across the globe, which hasn’t happened since 1944. In the year 2020 there will be a total of 13 full moons, which is also remarkable, as most years only have 12.