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Skywatchers in Austria and around the world can look forward to a celestial rarity at the end of the month. On 31 May 2026, the Moon will reach its full phase for the second time in May—a phenomenon known as a Blue Moon. Despite its name, the Moon will not appear blue, but the event remains special for several reasons.
Two Full Moons in One Month
The Moon is already prominent in the evening sky, but the highlight comes on 31 May at 10:45 AM, when it becomes full again. The unusual part: the first full moon of the month occurred on 1 May 2026.
A second full moon within a single calendar month is what astronomers call a Blue Moon. The term originates from the English expression “once in a blue moon”—meaning something that happens very rarely.
Why Blue Moons Are So Rare
A lunar cycle—from one full moon to the next—lasts about 29.5 days. For two full moons to fit into one month, the first must occur very early.
- Months with 31 days offer the best chance
- Months with 30 days make it unlikely
- In February, a Blue Moon is impossible due to its shorter length
This makes Blue Moons an infrequent treat, occurring roughly every 2.5 years.
February’s Oddity: No Full Moon at All
February can occasionally skip a full moon entirely. When that happens, both January and March feature two full moons each.
This last occurred in 2018 and won’t happen again until 2037.
The next Blue Moons after 2026 are expected on:
- 2 December 2028
- 1 September 2031
Not Blue—But Definitely Smaller
Although the name suggests otherwise, the Moon will not turn blue. But this Blue Moon has another twist: it will be a Minimoon, also called a Micromoon.
Because the Moon’s orbit is elliptical, its distance from Earth varies. In early June, it reaches the apogee, the farthest point in its orbit.
- On 1 June at 6:32 AM, the Moon will be about 406,366 km from Earth
- This makes the full moon appear slightly smaller and dimmer than a typical full moon
- The opposite effect—a larger, brighter full moon—is known as a Supermoon
A Rare Double: Blue Moon + Minimoon
The combination of a Blue Moon and a Minimoon is an uncommon pairing, making the night of 31 May 2026 especially noteworthy for astronomy enthusiasts, photographers, and anyone who enjoys watching the sky.
- source: 5minuten.at/picture: pixabay.com
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