What Is a Blue Moon and Where Did It Get Its Name?

This instance when the full moon is visible twice is known as “Blue Moon”. It’s possible that the blue moon tonight may actually appear red!

This is an astronomy story that comes up only once in a blue moon.

Some suggest that the term blue has nothing to do with color but with an old word “belewe” meaning to betray. Well, we’re sorry to be the bearers of bum news, but there are a few things you should know about this medium-rare occurrence.

If you see the moon tonight it will look impressively round – a full moon by any normal observer’s estimation. The Farmers’ Almanac pinned down the first mention of the phrase to 1824. There were two blue moons in three months in 1999. Twenty years later, Villa is one of the pioneers of the craft beer movement and Blue Moon has a lot to be proud of.

But here’s where the history of the idiom gets tricky: Defining “blue moon” as the second moon in a calendar month appears to date back to 1946 when amateur astronomer James Hugh Pruett defined it as such in an issue of Sky & Telescope magazine. Indeed, a blue moon is rare, occuring only once every three years. If a season has four full moons, then the third full moon may be called a Blue Moon.

When Keith Villa created Blue Moon Belgian White Belgian-Style Wheat Ale in 1995, he introduced beer drinkers across the country to Belgian-style beers with a creative twist. Another occurred on August 20-21, 2013. The last was in 2010, and the next one is expected in May 2016.

The full moon that will be seen in the sky Friday night is labeled by many as a “blue moon”, but what does that mean exactly?