Blue Moon on May 31, the smallest full moon of the year
Tonight's second full moon of May is also a micromoon, the smallest full phase of all 2026 because the Moon sits at apogee.
- Tonight, May 31, brings the second full moon within a single month, known as a blue moon.
- The same full phase is also a micromoon, the smallest and dimmest full moon of 2026.
- The Moon sits at apogee, its farthest point from Earth, so it looks smaller and paler.
- The name blue moon is a calendar convention, the Moon's color does not change.
Tonight, May 31, the sky offers a second full moon within the same calendar month, an event astronomers call a blue moon. May’s first full moon, also known as the Flower Moon, arrived on May 1, so this second full phase within thirty days closes a rare double bill.
The Moon reaches its exact full phase at 10:45 a.m. Eastern Time, though local observers will only see it after sunset. From Serbia, the disc rises about 45 minutes after the Sun goes down and can be watched with the naked eye under clear skies, low on the eastern horizon.
Why is this the smallest full moon of 2026?
This full phase coincides with apogee, the point where the Moon sits farthest from Earth along its elliptical orbit. That distance makes the lunar disc appear noticeably smaller and fainter than a full moon near Earth, which is why the event is called a micromoon.
Astronomers note that the size difference is hard to spot with the naked eye, yet it is measurable in photographs taken through the same lens across the year. According to the portal nebo.com.hr, this is a special occasion.
It will be the smallest full lunar phase of all 2026 because it sits at apogee.
This is also the thirteenth full moon of 2026. A calendar year usually holds twelve full moons, so the thirteenth appears only about once every two to three years, when the lunar cycle of roughly 29.5 days adds up to an extra full phase.
Does a blue moon really change color?
Despite the name, a blue moon has nothing to do with color. The term is purely a calendar label for the second full moon in a single month, with no effect on how the lunar light looks.
The Moon will not change its color, it is only paperwork.
The Moon can take on a bluish tint only in rare conditions, when dust or smoke particles of a particular size scatter light in a specific way. Those effects are tied to large wildfires or volcanic eruptions, not to the calendar.
No equipment is needed to watch tonight. A clear sky and a glance toward the east shortly after sunset are enough, while binoculars or a small telescope will reveal fine detail across the Moon’s craters and seas.
Will you step outside tonight to catch the smallest full moon of the year?
