Tonight’s sky will be graced by a “blue moon.” It is the first blue moon since New Year’s Eve 2009. The next blue moon won’t appear until July 2015. Tonight’s full moon won’t actually be blue for most of us. A “blue moon” is commonly defined as the second full moon in a calendar month. It doesn’t happen often and so is the inspiration for the phrase, “once in a blue moon.”
It is possible that there may be a literally blue moon for some. Ash in the atmosphere from forest fires or volcanic eruptions can make the moon appear to be tinted blue. There are a sufficient number of forest and brush fires in parts of the United States resulting from recent drought conditions so that tonight’s moon may be blue in both senses.