A Blue Moon is a rare occurrence of either the second full moon in a single calendar month (called a calendrical or monthly Blue Moon) or the third full moon in an astronomical season that has four full moons (called a seasonal Blue Moon). The next Blue Moon events are:

• The next calendrical (monthly) Blue Moon will be on May 31, 2026.
• The next seasonal Blue Moon will be on May 20, 2027.

Blue Moons occur about once every 2.5 to 3 years on average. The term "Blue Moon" does not refer to the actual color of the moon, which remains pale gray or white, although rare atmospheric conditions can make the moon appear blue.