Blue Moon August 2012: Catch It Friday the 31st or Next One in 2015

The next blue moon will occur on Friday, August 31, 2012.  If you miss this one, the next time you can catch another blue moon is in July 2015.  The moon is expected to be its fullest in the United States at 9:58 a.m. EST.  

What exactly is a blue moon?  The moon is not actually blue in color.  

According to the Merriam Webster dictionary, it is "a second full moon in a calendar month".  It is essentially an extra full moon in a full season.  Every season usually have three full moons.  If the season has a fourth full moon, the blue moon refers to the third full moon.

A blue moon occurs on average every 2.7 years.  Some years have a double blue moon with the last one that occurred in 1999.  The next double moon is expected to display in the year 2018.

The popular phrase "once in blue moon" refers to something being rare.  Do you plan on catching the blue moon on Friday or waiting until 2015 to see another blue moon?