And although Tuesday’s full moon will be just the first full moon in August — typically, when a Blue Moon occurs, there are two full moons per month — there are several other meanings for the term, according to Space.com.
A less common usage dates back to at least 1937, according to Space.com, in which a Blue Moon is the third of four full moons each season. In that case, a season is the time from the equinox to the solstice, or from the solstice to the equinox.
Tuesday’s Blue Moon, then, is what’s known as a "seasonal" blue moon: The third this summer season.
The rarest Blue Moon is a phenomenon in which the moon actually looks … wait for it … Yes, blue. This is caused by particles in the air — often ash and dust caused by a volcano or, as in this instance described on Spaceweather.com, a major forest fire. "It was a cloudy day. Early in the afternoon, the sun disappeared and it became as dark as midnight...We had no Television at the time, but heard over the radio that there was a forest fire in Canada producing so much smoke that it had blacked out the sun … … As the day waned, the smoke thinned a bit and the sun could be seen through the blackness as a faint blue orb, but it never did get light outside. After nightfall the moon which was full that night, was blue. I read later that blue moons were seen as far away as Europe on Sept. 26, 1950." (Read this and other Blue Moon stories at Spaceweather.com).
So why not step outside and look up anyway? No matter what color, a full moon is always a magnificent sight.