Seasonal Blue Moons take place slightly less frequently than monthly Blue Moons—in the 1100 years between 1550 and 2650, there are 408 seasonal Blue Moons and 456 monthly Blue Moons. This means that either type of Blue Moon occurs roughly every two or three years.
Blue Moons that are blue are incredibly rare and have nothing to do with the calendar or the Moon's phases but are instead a result of atmospheric conditions. Volcanic ashes and smoke, water droplets in the air, or certain types of clouds can all contribute to a Full Moon taking on a blue shade on rare occasions.
The Moon can sometimes look red
Double Blue Moon
Because of this, February, which has 28 days in a Common Year and 29 days in a Leap Year, can never have a monthly Blue Moon. Some years, February has no Full Moon at all, which is called a Black Moon. A February with no Full Moon happens when January and March have a Blue Moon each.
Known as a Double Blue Moon, this phenomenon is rather uncommon and takes place only about three to five times in a century. We saw a Double Blue Moon in 2018 in most time zones and will see it again 19 years later, in 2037, in many time zones.
Astronomical terms & definitions
Seasonal and Monthly Blue Moons Together
Seasonal and monthly Blue Moons can also sometimes occur in the same year. Between 1550 and 2650, 20 years have one seasonal and one monthly Blue Moon in many time zones. The last time this happened was in 1934 and the next time will be in 2048.
In the same period, 21 years have Triple Blue Moons—one seasonal and two monthly Blue Moons in the same calendar year. The next is in 2143, while the last time was in 1961.
Two seasonal Blue Moons in a year is an impossibility, as that would require 14 Full Moons in the same year.
How can Full Moon be in the daytime?
Not the Same Worldwide
The Moon reaches its various phases at specific moments. But because of time zones, the local time of a Full Moon can differ from one location to another. For instance, the Blue Moon in 2026 takes place at 08:45 UTC on May 31. Locations in time zones that are at least 9 hours behind UTC, such as Honolulu, will see their Full Moon take place on May 30, 2026.