May 31 Full Moon Peaks as Rare Blue Micromoon, Appearing 10% to 15% Smaller
Updated
Updated · National Geographic · May 27
May 31 Full Moon Peaks as Rare Blue Micromoon, Appearing 10% to 15% Smaller
11 articles · Updated · National Geographic · May 27
8:45 a.m. UTC on May 31 marks peak illumination for a full moon that carries the rare double label of a blue moon and a micromoon.
The blue-moon tag comes from May hosting its second full moon, while the micromoon label reflects the moon reaching full phase near apogee—its farthest point from Earth.
That extra distance makes the moon look slightly smaller and dimmer than usual, with the apparent diameter roughly 10% to 15% smaller than a Supermoon.
May 30 moonrise or the early hours of May 31 offer the best viewing, especially low on the eastern horizon; binoculars or photos can make the subtle difference easier to spot.
Blue moons occur every two to three years despite the phrase "once in a blue moon," and the next supermoon comparison point arrives on Dec. 24, 2026.
The upcoming 'Blue Moon' will actually glow orange. What rare event could make the moon truly appear blue?
This weekend's Blue Moon is the year's smallest, so why might it appear deceptively huge on the horizon?
Our modern 'Blue Moon' definition came from a mistake. What was the historical error that created this celestial event?