Mark Your Calendars: The Next Blue Moon Arrives on May 31, 2026

The next Blue Moon, a rare celestial event, is set to occur on May 31, 2026. This phenomenon refers to the second full moon within a single calendar month, a result of the lunar cycle lasting roughly 29.5 days. While most years feature 12 full moons, the slight mismatch between the lunar cycle and the calendar year leads to the appearance of a 13th full moon approximately every two to three years, earning the name “Blue Moon.”

Types of Blue Moons

According to NASA, there are two types of Blue Moons: seasonal and monthly. A seasonal Blue Moon is the third full moon in a season that has four full moons. In contrast, a monthly Blue Moon occurs when two full moons fall within the same calendar month. The upcoming Blue Moon in May 2026 will be a monthly Blue Moon.

Despite its name, the moon doesn’t turn blue during this event. The term originated from historical usage and has come to symbolize these infrequent lunar occurrences.

Past and Future Blue Moons

The most recent Blue Moon took place on August 19, 2024. Though rare, Blue Moons follow a predictable pattern based on the alignment of lunar phases with the Gregorian calendar. The next seasonal Blue Moon is expected on August 21, 2032.

Can the Moon Appear Blue?

While the moon typically doesn’t change color during a Blue Moon, atmospheric conditions can occasionally give it a bluish hue. Events such as volcanic eruptions, like Krakatoa in 1883, or large-scale forest fires can scatter red light in the atmosphere, making the moon appear blue. These occurrences, however, are extremely rare and unrelated to the Blue Moon phenomenon.