The rare event -- the second full moon in a calendar month -- occurs Friday night.
Once every "two to three years" do the phases of the moon -- when the Earth's satellite goes from full to new -- line up with the beginning and end of the calendar month, according to astronomist Jonathan Braidman at the Chabot Space and Science Center in Oakland in an interview with the online San Francisco Appeal.
The last time there was a blue moon was in March 2010. The next time will be July 2015, with full moons on July 2 and July 31, the newspaper reported.
The bright, full moon will be directly overhead at midnight, according to Bob Jacobs, a NASA spokesman. This will give moon-gazers a prime opportunity to see for themselves where NASA astronauts landed in 1969. Meterologists are hoping you can see it though; there are clouds in the forecast.
If you believe that the moon's surface looks like a human face, the spot where Apollo 11 astronaut Neil Armstrong -- who died last week at 82 -- landed is the "moon's right eye," according to Braidman. Armstrong's wife has asked the nation to go outside tonight to wink at the moon in honor of her husband, who died last week.
Visit the Chabot Space and Science Center for free moon viewings tonight and Saturday.