This weekend, the skies in the United States will be graced with a rare blue moon.

Attention, sky gazers: This weekend offers more than a brief vacation from the workweek’s concerns. As a bonus, a rare seasonal blue moon will be visible.

On Sunday, the night sky will be adorned by a blue moon. October 31, 2020 was the date of the last seasonal blue moon.

A “blue” moon occurs twice a year. A blue moon occurs when there are two full moons in a calendar month. Second, according to The Farmers’ Almanac, it’s termed the “Blue Moon.”

On August 22, the sky will be illuminated by a seasonal blue moon. Any time there are four full moons in a season, there is a “blue moon.”

According to The Farmers’ Almanac, this definition is more legend than fact.

• 

Blue moons are named after a misreading of an essay authored by James Hugh Pruett in the March 1946 edition of “Sky & Telescope.” While writing “Once in a Blue Moon” for the Maine Farmers Almanac, Pruitt misrepresented what he read.

As for a blue moon, that’s a term that refers to the number of full moons in a single season, which we’ll experience on Sunday. Full moons occur on average every 12 months or three every season. If there are four full moons in a season, the third one is called a “blue moon.”

There will be another chance to see a full blue moon in only three years, so don’t miss out.

After then, the next seasonal blue moon will appear on Aug. 19, 2024, and the following one will appear on May 20, 2027.

A blue moon, then, is it genuinely blue? According to EarthSky.org, this isn’t the case.

Most likely, the photo of a blue moon that you’re looking at has been taken using a blue lens filter. On rare occasions, generally after massive forest fires or big volcanic eruptions, The Farmers’ Almanac reports that the moon has taken on a blue or purple colour. When soot and ash particles are driven into the Earth’s atmosphere, the moon might seem blue at times.

Having said that, a full moon in any month or season is unlikely to seem blue.

It is also a sure indicator of fall, according to the website EarthSky.org.

Due to its proximity to the fall equinox, Sunday’s blue moon is similar to September’s harvest moon. It is the closest full moon to the fall equinox, hence it is called the harvest moon by definition On September 20, the full harvest moon will appear.