Its second occurrence in a month will be the last for nearly three years.
This is a special month for romantics and werewolves. August is about to have its second full moon.
As No. 2, the full moon that rises Friday will be called a blue moon. There's nothing scientifically significant about the event, although consumption of Blue Moon Beer is likely to jump that night, as are calls to oldies stations requesting the song "Blue Moon." And if you made a promise to do something "once in a blue moon," you better get ready to follow through on the pledge.
Although we think of full moons as happening once a month, the moon isn't completely in sync with our calendar. A full moon occurs about once every 29 days. The last one was Aug. 2.
"It's just an aberration caused by the calendar not matching the moon's cycle," said Kisha Delain, a professor in the University of St. Thomas physics department. "But that doesn't mean that it stops being culturally interesting or that we can't have some fun with it."
There are several legends about how the blue moon moniker came about. The most commonly cited one is that a year's typical 12 moons originally were named to reflect the season they appeared -- only the "harvest moon" label still sticks -- and when an extra moon horned in, it was called a blue moon to keep all the other moons in their regular spots.
If you miss this blue moon, there will be another one in July 2015. If you're really the patient sort, mark your calendars now for Dec. 31, 2028. That night will feature a blue moon combined with a total lunar eclipse.