Blue Moon Coming Soon!

Blue Moon – 31st July 2015

By Eric Elwell, StormCenter 7 Chief Meteorologist
Re-blogged from http://www.whio.com/

So have you ever told someone that “it only happens once in a blue moon?”

Well, that blue moon is about to happen next week! Actually a week from tomorrow on July 31.

But the moon will not actually be blue. And we aren’t talking about the adult beverage either. So what really is a blue moon?

There are actually two definitions of a Blue Moon in astronomy; both are a type of full moon. (If the moon actually looks blue, it’s caused by a rare type of dust in the atmosphere.)

The term “once in a Blue Moon” means that that something is rare. But just how rare depends on your definition.

In astronomy, a Blue Moon is a full moon, which doesn’t quite fit in with the months in our calendar. However, there are two different ways of calculating which full moon is a Blue Moon.

1) Blue Moon = The third full moon in an astronomical season with 4 full moons (versus the normal 3)

2) Blue Moon = The second full moon in a month with two full moons.

That being said … the correct, original definition is that a “Blue Moon” is the third full moon in an astronomical season with four full moons. A normal year has four astronomical seasons — spring, summer, fall and winter — with three months and normally three full moons each. When one of the astronomical seasons has four full moons, instead of the normal three, the third full moon is called a Blue Moon.

So now you know! (or are you more confused?)