Top line
The so-called Blue Moon rose at sunset on Saturday, May 30, marking the second full moon of the month and concluding a rare calendar phenomenon. May began with the Flower Moon on May 1 and ended with this second full moon—an event that only occurs once every two to three years, as the Moon's 29.5-day cycle sometimes occurs twice within a single calendar month. Here are all the best Blue Moon photos from around the world.
The full Blue Moon rises over Visa headquarters and the Metro Center mall in Foster City, California, on May 30, 2026. (Photo: Typhoon Coskun/Anadolu via Getty Images)
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Key facts
The full moon occurred at 4:45 a.m. ET on Sunday, March 31, but was best viewed at moonrise at twilight the night before, Saturday, March 30.
The second full moon in a single calendar month will not occur again until December 31, 2028. They occur approximately every 2.5 years.
The next astronomical event will be a very close encounter of two bright planets, Jupiter and Venus, in the sky after sunset from June 9 to 11.
The moon rises behind the Eiffel Tower the day before the full Blue Moon as people celebrate on the roof of a truck after Paris Saint-Germain (PSG) beats Arsenal in the Champions League final on May 30, 2026, in Paris, France. (Photo by Gary Hershorn/Getty Images)
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Why was the "blue moon" orange at sunrise?
To many observers, the blue moon appeared not blue, but orange. This is because when the moon is close to the horizon, its light passes through a thicker layer of the Earth's atmosphere. Shorter wavelengths are scattered, leaving warmer hues—orange when the moon appears close to the horizon, then yellow as it rises. At the same time, a lunar illusion makes the moon appear larger against foreground objects such as buildings, trees, or distant hills. As the moon rose higher, these effects disappeared, and it returned to its usual pale white appearance.
On the evening of May 30, 2026, a full Blue Moon will rise over an electrical tower near Kehnec, eastern Slovakia. A Blue Moon is a phenomenon where four full moons occur within a single astronomical season, making it a relatively rare celestial event. The previous seasonal Blue Moon was observed on August 19, 2024, and the next one is expected on May 20, 2029. (Photo by Robert Nemethy/Anadolu via Getty Images)
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Two types of blue moons«
Despite its name, a "blue moon" has nothing to do with color. Most often, the term refers to the second full moon in a calendar month, as occurred in May 2026. Since full moons occur approximately every 29.5 days, most months only have one full moon, but occasionally two occur. This "monthly blue moon" occurs approximately every two to three years. The next one will occur on December 31, 2028—a particularly rare occurrence that will also coincide with a total lunar eclipse, also known as a "blue moon." However, there is also a second definition—a seasonal blue moon, which is the third full moon in an astronomical season containing four full moons. The next such full moon will occur on May 20, 2027.
A full blue moon rises over palm trees in Foster City, California, on May 30, 2026. (Photo: Typhoon Coskun/Anadolu via Getty Images)
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Why did the "blue" moon seem small?
This particular blue moon also had one peculiarity: it was the smallest full moon of 2026. Situated close to its apogee, the point in its orbit farthest from Earth, it appeared slightly smaller and dimmer than average—a so-called micromoon. The moon was approximately 50,000 kilometers farther from Earth than during a typical supermoon, reducing its apparent size and brightness.
A blue moon rises over San José de Maipo, a suburb of Chile's capital, Santiago, on Saturday, May 30, 2026. (AP Photo/Esteban Felix)
© 2026 Associated Press. All rights reserved.
What causes a full moon?
A full moon occurs when the Earth passes directly between the Sun and the Moon, allowing sunlight to fully illuminate the side of the Moon facing us. From our perspective, the lunar disk appears full—a bright, round globe that rises at sunset and sets at sunrise. The Moon doesn't emit its own light—it simply reflects sunlight—and is always half-illuminated by the Sun, just like the Earth. During a full moon, the illuminated half faces the Earth, allowing us to see it fully illuminated.
A blue moon rises behind the cross over the Church of Apostle Andrew, a Russian Orthodox church in Episkopeio, on the outskirts of the capital of Cyprus, Nicosia, Saturday, May 30, 2026. (AP Photo/Petros Karadjias)
© 2026 Associated Press. All rights reserved.
Why do we only see one side of the Moon?
We always see the same side of the Moon because it is tidally locked to Earth. It rotates once on its axis in the same amount of time it takes us to orbit the planet—about 27.3 days—so one hemisphere always faces us. Although the Moon orbits Earth every 27.3 days, the interval between full moons is longer—about 29.5 days. This is because Earth also orbits the Sun. After completing one orbit, the Moon must travel a slightly greater distance to again achieve the same alignment with the Sun and Earth, creating the familiar cycle of lunar phases.
Further reading
FORBES | By Jamie Carter In Pictures: A full 'flower moon' lights up night skies around the world.
FORBES | By Jamie Carter What's that bright star in the west after sunset?
FORBES | By Jamie Carter There are 100 days left until the total solar eclipse. Here's how to see it.
This article was originally published on Forbes.com.