You might want to avoid the phrase “once in a blue moon” for a little while.
The next full moon will happen Sunday, May 31 – and this time around, it’s a blue moon, according to The Old Farmer’s Almanac.
The blue moon will also be a micromoon, which means it will appear smaller and dimmer than a typical full moon. The moon reaches its farthest orbit from the Earth on June 1 and will be high in the sky, making it appear farther away.
The National Weather Service forecast for Sunday evening calls for partly cloudy conditions with no rain. Milwaukee’s Clear Sky Chart anticipates cloud cover to hover between 70% and 80%.
Why is it called a blue moon?
Similar to some other lunar phenomenon, a blue moon is not actually blue.
The name simply refers to any second full moon in one month. Typically, every month only has one full moon. Full moons are named by their corresponding month. So, when a month has two full moons, the second is always blue.
The origin of calling a month’s second full moon the blue moon is somewhat obscured. One of the latest dated record of the practice was in James Hugh Pruett’s “Once in a Blue Moon” article for Sky and Telescope in 1946, but he notes he saw references to blue moons in almanacs as far back as 1937.
The idiom used to be “the moon is blue” and mean an occurrence that was totally impossible, according to the Encyclopedia Britannica. That changed in 1883 after the eruption of Krakatoa in Indonesia. In the two years following the eruption, people around the world reported strange colored sunsets and a moon with a blue hue. Since then, the idiom “once in a blue moon” became a term meaning rare but possible.
What are the best places in Wisconsin to view the night sky?
Here is a list of Wisconsin locations that could offer some of the best views of the night sky.
What’s the 2026 full moon schedule?
Here is the 2026 full moon schedule for the rest of 2026, according to The Old Farmer’s Almanac.
This article originally appeared on Milwaukee Journal Sentinel: A blue moon is coming May 31. Here’s what to know in Wisconsin
Reporting by Caden Perry, Milwaukee Journal Sentinel / Milwaukee Journal Sentinel
USA TODAY Network via Reuters Connect
