A Rare August Blue Moon Will Illuminate the Sky This Weekend

A Rare August Blue Moon Will Illuminate the Sky This Weekend
  • This year's August full moon is a rare seasonal blue moon and will reach peak illumination on Sunday, August 22 at 8:02 a.m. EDT.

  • This type of blue moon only rises about once every two to three years.

  • This blue moon is different from the more commonly known one (with the same name) that marks the second full moon in one month. Neither are actually blue in color.


Blue moons are already rare, but the one that will rise this weekend—the 2021 August blue moon—is even more special. So dust off your telescope and get ready for a spectacular view.

Here's the thing: The term "blue moon" actually has two definitions, per NASA. The first: It's the second full moon that occurs within a calendar month (because each month typically only has one full moon). And second: it's the third full moon to rise within a calendar season that has four full moons (as opposed to the usual three). Typically, each calendar season consists of three months and therefore, three full moons.

But this summer, which began on June 20 and ends September 22, will have four, making August's full moon a seasonal blue moon. According to EarthSky.org, this type of blue moon only rises about once every two to three years. Unfortunately, neither type of blue moon is actually blue in color.

But wait, there's more! August's blue moon is not only a semi-rare occurrence, but it will also be uniquely long and bright. Although it will reach peak illumination on Sunday, August 22 at 8:02 a.m. EDT, it will rise with an almost equal glow each evening from Friday, August 20 to Monday, August 22, making it a full moon weekend—giving you extra time to marvel at its enchanting sparkle.

When August's full moon doesn't fall into the special spot that it has this year, it's referred to as the full sturgeon moon, named after the large fish that were easily caught by indigenous Algonquin tribes in the Great Lakes this time of year. The moon is also known as the full red moon, the green corn moon, or the grain moon, according to Farmer's Almanac.

If you miss this full moon, don't worry there are more to come—though they'll be different. The next full moon, the harvest moon or the full corn moon, will rise on September 20, per Farmer's Almanac. To track when the sun will set in your area so you can best prepare for viewing, try The Old Farmer’s Almanac sunrise and sunset calculator.

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