Blue Moon: When Is the Next One?
The next Blue Moon is on : a seasonal Blue Moon, the third full moon of a season with four.
- Seasonal Blue Moon
- Moon in Scorpio
The next monthly Blue Moon, a second full moon in one calendar month, is on .
The last Blue Moon was on May 31, 2026, the second full moon of May 2026.
Blue Moons 2020–2040
Monthly Blue Moons are counted in UTC; in time zones west of UTC a full moon shortly after midnight UTC can fall on the previous calendar day, which moves a Blue Moon by a month in some years.
Two definitions
A Blue Moon has two accepted meanings, and this site lists both.
The monthly Blue Moon is the second full moon in a calendar month. Because the lunar cycle is 29.53 days, a full moon on the first or second day of a 30- or 31-day month leaves room for another at the end. It happens about every two and a half years, and the dates depend on the time zone: a full moon at 1 AM UTC on the first of the month is still the last day of the previous month in the Americas.
The seasonal Blue Moon is the older definition: the third full moon in an astronomical season that has four. A season between a solstice and an equinox usually holds three full moons; when it holds four, the Maine Farmers’ Almanac called the third one blue, so that the names of the other full moons stayed in their usual places. The monthly meaning comes from a 1946 article in Sky & Telescope that misread the almanac rule, and the mistake caught on.
Is the Moon blue?
No. A Blue Moon is the ordinary silver-white of any full moon. The Moon can look blue only when the air is full of fine particles of a particular size, after large volcanic eruptions or forest fires: it happened after Krakatoa in 1883 and over North America after Canadian forest fires in 1950. The phrase “once in a blue moon” means something rare, and it is older than either calendar definition.
In lunar tradition
Folk tradition gives the Blue Moon no rules of its own; it follows the same guidance as any full moon on the full moon pages. On this site the name Blue Moon goes to the second full moon of a month, with the month’s traditional name belonging to the first; the full moon names page explains the convention.
Keep exploring
- Full moon names
What the first full moon of each month is called
- Supermoon
The closest full moons of the year
- Blood moon
Total lunar eclipses and why the Moon turns red
- Next full moon
Countdown and the full moon calendar
Frequently asked questions
When is the next blue moon?
The next Blue Moon is on Thursday, May 20, 2027, at 10:59 AM UTC, a seasonal Blue Moon, the third full moon of a season with four. The next monthly Blue Moon, a second full moon in one calendar month, is on December 31, 2028.
What is a blue moon?
A Blue Moon is a second full moon in one calendar month, the common modern definition, or, in the older almanac definition, the third full moon in an astronomical season that has four instead of the usual three. Either way it is an ordinary full moon; the name is about the calendar, not the color.
How often does a blue moon happen?
A monthly Blue Moon comes about every two and a half years, because 12 lunar cycles of 29.53 days fall about 11 days short of a calendar year and the extra full moon eventually lands in a month that already has one. Seasonal Blue Moons come at a similar rate, so a Blue Moon of one kind or the other happens roughly every one to two years.
What does a blue moon mean?
The phrase “once in a blue moon” means something rare, and that is the only meaning the calendar gives it. Folk tradition has no separate rules for a Blue Moon: in lunar gardening and hair tradition it follows the same guidance as any full moon.
Is a blue moon actually blue?
No. A Blue Moon looks like any other full moon. The Moon can appear blue only when the air holds fine particles of just the right size, as after the Krakatoa eruption of 1883 or the Canadian forest fires of 1950, and that has nothing to do with the calendar.
When was the last blue moon?
The last Blue Moon was on Sunday, May 31, 2026, the second full moon of May 2026.