Once in a Blue Moon

Look to the sky Friday to see a "blue moon." 

But don't expect to see the color blue. A blue moon refers to the rarity of multiple full moons in a month or season. Friday's full moon will be the second in August. The first took place on Aug. 1. 

Two full moons in a month typically occurs every 2.7 years, according to the Huffington Post. 

The last blue moon was on Dec. 31, 2009, and the next won't occur until 2015.

Best time to see the Blue Moon: The moon will be at its fullest at 8:58 a.m. CST, according to the Farmers' Almanac. 

And if you're looking for a special way to celebrate the rare, celestial site, a blog by the Lake Michigan Swimmers said they will celebrate with a Blue Moon beer toast at at 6:30 p.m. followed by a Lake Michigan swim.