This month's full moon, which rises on Tuesday (August 20th) is not just a Blue Moon - it's also the full Sturgeon Moon, the Full Red Moon, the Green Corn Moon and the Grain Moon. Today's full moon qualifies as a Blue Moon because it's the third full moon in the season with four. A 1946 article in "Sky & Telescope" magazine mistakenly defined a blue moon as the 2nd full moon in a single month (since moth months have only one full moon), and it stuck.
Although August only has one full moon, tonight's qualifies as the third full moon in a four-full-moon season. Both Native Americans and early European settles added their own names for the full moons to the lexicon. The annual August full moon has come to be known as the Full Sturgeon Moon, because sturgeon can most easily be caught at this time of year according to native tribes in the Great Lakes region. Another name is the Full Red Moon because the weather conditions can make it look reddish when it rises. And finally, because crops grow tall at this time of year, the moon is also known as Green Corn Moon or Grain Moon.