First 'seasonal blue moon' in three years happens this weekend

It's the third full moon of the season

By Chris Michaels - Meteorologist

ROANOKE, Va. - We've all heard the saying "once in a blue moon." Did you know, though, that there are two different meanings to a blue moon?

Neither actually involves the moon turning blue.

One definition of a blue moon (monthly blue moon) is the second full moon of the month. Another definition of a blue moon, and equally as accurate, is the third full moon of a season with four full moons (seasonal blue moon). 

This weekend, our third full moon of the season will come. This is called the 'seasonal blue moon,' and it is the first one since May 21, 2016. 

Again, we reiterate...it will not actually turn blue.

The next blue moon doesn't come until Halloween of 2020. That will be the second full moon of the month. The next seasonal blue moon won't come until August of 2021.

On average, a blue moon happens once every 2 years, 150 days. A seasonal blue moon, on average, happens once ever 2 years, 248 days.

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