In the night of May 30–31, 2026, the full Moon will draw eyes to the sky. It will be nicknamed a “blue Moon” because it will be the second full Moon of May. A rare calendar phenomenon, easy to observe with the naked eye if weather cooperates.
Why do we talk about “blue Moon”?
On Sunday, May 31, 2026, the Moon will be full at 10:45 a.m., Paris time. The exact moment will thus fall in the middle of the day for mainland France, but the spectacle will unfold mainly in the night sky: the Moon will appear almost perfectly full during the night from Saturday night into Sunday, May 30–31, and again on the evening of Sunday, May 31. The US Naval Observatory fixes the full Moon at 08:45 UTC, i.e., 10:45 in France, and confirms that a first full Moon already occurred on May 1, 2026.
The name is misleading. A blue Moon isn’t a Moon that turns blue. In today’s common usage, it refers to the second full Moon occurring during the same calendar month. This is the case in May 2026: the first full Moon of the month occurred on May 1, and the second will occur on May 31.
This shift stems from the fact that the lunar cycle lasts about 29.5 days, while our calendar months have 28 to 31 days. From time to time, if a full Moon lands right at the start of a 30- or 31-day month, a second can occur just before the month ends. The Royal Observatory Greenwich notes that this misalignment between the solar calendar and the lunar cycle makes the appearance of more than one full Moon in a single month possible. NASA explains that the term “blue Moon” historically referred to that “extra full Moon,” and that the modern usage—the second full Moon in a month—has spread since the 1940s.
What will we really see in the sky?
Visually, don’t expect a bluish Moon. The Moon will look like a typical full Moon: a very bright disk, white to silver when high in the sky, sometimes yellow, golden, or orange near the horizon. That color near the horizon is a classic atmospheric effect: the light travels through a greater thickness of air, scattering shorter wavelengths more.
Interestingly, this full Moon on May 31, 2026 will also be a micromoon: it will occur when the Moon is near apogee, its farthest point from the Earth. EarthSky even calls it the farthest full Moon of 2026, at about 406,135 km from Earth. It should therefore appear slightly smaller and a bit dimmer than an average full Moon, but this difference will be subtle to the naked eye.
When to observe it in the United States?
The best time will be the night of Saturday, May 30 into Sunday, May 31, 2026, after sunset. On May 30 in New York City the Moon will rise around 3:34 p.m. and will set around 11:44 p.m.; the following evening, it will rise around 4:37 p.m. and stay nearly full. Times will vary by region, with the Moon rising earlier on the East Coast and later on the West Coast. In Los Angeles, for example, you can expect Moonrise to occur in the early afternoon on May 30 and again in the mid-afternoon on May 31, with similar near-full brightness across the night.
Can the Moon really turn blue?
Very rarely, yes—but that won’t be tied to the calendar blue Moon phenomenon. A genuinely blue-tinged Moon can appear if the atmosphere contains smoke or dust particles of a particular size, for example after a major volcanic eruption or widespread fires. EarthSky notes that such blue moons have been observed after events like the Krakatoa eruption in 1883 or the Mount St. Helens eruption in 1980.
