Special Moon Events - 2026
Blue Moon 2026
The next blue moon falls on Sunday, May 31, 2026 - the second full moon in one calendar month. Here's what that actually means, and how blue moons differ from blood moons and supermoons.
What is a blue moon?
Modern definition (most common): the second full moon in a single calendar month. Because the synodic month is 29.53 days and most calendar months are 30-31 days, a second full moon can squeeze into the same month - that's a blue moon.
Seasonal definition (original, older): the third full moon in a season that contains four full moons. Under this definition the moon does not turn blue either - the name simply marks an 'extra' full moon in the calendar.
Either way, the moon keeps its normal color. A genuinely blue-looking moon is a rare atmospheric phenomenon caused by large particles (volcanic ash or wildfire smoke) that scatter red light - unrelated to the calendar event.
| Term | Definition | Next / 2026 date |
|---|---|---|
| Blue Moon (modern) | 2nd full moon in one calendar month | May 31, 2026 |
| Blue Moon (seasonal) | 3rd full moon in a season with 4 | Roughly every 19 years |
| Blood Moon | Full moon during a total lunar eclipse (appears red) | March 3, 2026 (total) |
| Supermoon | Full moon near perigee - appears larger & brighter | See full moon calendar |
Special moon events in 2026
All dates verified against the NASA eclipse catalog and Meeus' algorithm.
May 31 - Blue Moon
The second full moon of May 2026 (the first is May 1). It is a regular full moon in every astronomical sense - only the calendar makes it special.
March 3 - Total Lunar Eclipse (Blood Moon)
Earth's shadow completely covers the full moon; refracted red light tints it red. Visible across Europe, Africa, Asia and Australia.
Aug 28 - Partial Lunar Eclipse
Part of the full moon enters Earth's umbra - the moon appears partially darkened. Visible in Europe, Africa and the Americas.
Feb 17 & Aug 12 - Solar Eclipses
These happen at new moons (Feb 17 annular, Aug 12 total) and are the solar counterparts to lunar eclipses.
Why blue moons happen
A full moon occurs roughly every 29.53 days (synodic month). Calendar months are 30 or 31 days, so there is a small 'overflow' each month. On average, once every 2.5-3 years this overflow aligns so that one calendar month contains two full moons - the first on the 1st or 2nd, the second on the 30th or 31st.
The last blue moon under the modern definition was August 2023. After May 2026, the next one will be in May 2029 - a roughly 3-year gap, typical for blue moons.
Note: different sources define the 'seasonal blue moon' (third of four full moons in a season) as the original meaning. Sky & Telescope popularized the modern 'second in a month' meaning in 1946 - both are in common use today.
Frequently asked questions
When is the next blue moon?
The next blue moon (modern definition: the second full moon in a calendar month) is May 31, 2026. The previous one was August 2023.
What does 'blue moon' actually mean?
The modern meaning is the second full moon in one calendar month - possible because the synodic month (29.53 days) is shorter than most calendar months. The older, seasonal definition is the third full moon in a season that has four full moons.
Why is the moon not actually blue?
The name is historical, not literal. The moon does not turn blue at a blue moon. A genuinely blue-looking moon is a rare atmospheric effect caused by smoke or ash particles (e.g. after large volcanic eruptions) scattering red light.
What is a blood moon?
A blood moon is a total lunar eclipse: Earth's shadow falls on the full moon, and only red wavelengths (refracted through Earth's atmosphere) reach it, so the moon appears reddish. In 2026 there is a total lunar eclipse on March 3.
Is a blue moon rare?
Under the modern definition, a blue moon happens roughly every 2.5 to 3 years. Under the seasonal definition it is rarer - about once every 19 years (within a Metonic cycle).
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