Blue Moon

May's Full Moon goes by several names, including the Full Flower Moon, the Full Corn Planting Moon and the Milk Moon. But this year, it will also go by the title of a Blue Moon.

A Blue Moon typically occurs once every few years (hence the term 'once in a Blue Moon') and is commonly the name of the second full moon in a calendar month. However, this weekend's Blue Moon gained its name a different way.

Normally, there are only three full moons in each season, but occasionally there is a season with four full moons. When this happens, like how it is this spring, the third of the four full moons earns the name of a Blue Moon.