If the clouds part enough this evening, make sure you look up and check out tonight's blue moon!
For more than half a century, whenever two full moons appear in a single month, the second full moon is deemed a 'blue moon'. But, this blue moon is considered a blue moon since it is the third of four full moons to occur this spring. Most seasons have just three full moons. The first this spring occurred just after the vernal equinox March 23, and the last occurs hours before the summer solstice on June 20.
This blue moon is also called the Full Flower Moon, because it means that the summer flowers will soon be blooming.
And just for the record: a blue moon is not actually blue. It is mostly bright white but can take on a bluish hue depending on the season and conditions.