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Rare Blue Moon of August 2021 rises tonight. Here's what to expect.

The August full moon rises tonight (Aug. 22), bringing skywatchers a rare seasonal "Blue Moon." 

The full moon, also known as the "Sturgeon Moon," reaches its peak Sunday morning at 8:02 a.m. EDT (1200 GMT). For New York City observers, the full moon will rise at 8:47 p.m., after the sun sets at 7:45 p.m. local time that day. However, it will appear large in the sky throughout both Saturday and Sunday nights, according to The Farmers' Almanac.

Full moons occur when the moon is exactly on the opposite side of the Earth from the sun. Generally, a full moon occurs 12 times in a year, or three times for each of the four seasons. 

Related: The August 2021 full moon is a Blue Moon. Here's why.

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Photographer Jenny Carter of Plano, Texas spied the Blue Moon full moon of July 2015 hiding behind some clouds while skywatching on July 31, 2015. (Image credit: Jenny Carter /Jenny Carter Photographer)

While the term Blue Moon is commonly reserved for the second full moon of a calendar month, August's Sturgeon Moon is considered a Blue Moon based on an older definition of the term, which represents the third full moon that occurs in a single season — in this case, summer — that has four full moons, according to a full moon guide from NASA

"The first recorded use of 'Blue Moon' in English dates from 1528," NASA's Gordon Johnston wrote in the full moon guide for August and September. "Speculations on the origin of the term include an old English phrase that means 'betrayer moon' or a reference to rare events, such as when dust in the atmosphere makes the moon actually appear blue. Since the 1940's the term Blue Moon has also been used for the second full moon in a month that has two full moons." 

It was not until the 1940's that the term "Blue Moon" was used to describe the second full moon in a month that has two full moons, according to the NASA statement.

August's full moon is traditionally called the Sturgeon Moon, after the giant sturgeon fish of the Great Lakes and Lake Champlain, which were most readily caught during this time of the summer, according to The Farmers' Almanac.

Related: Full moon names (and more) for 2021

However, this month's full moon also has a few other monikers, including the Flying Up Moon, which stems from the Cree of Ontario in reference to August being the time of year when young birds are finally ready to learn to fly. According to The Farmers' Almanac, other names include the Corn Moon, the Harvest Moon, the Ricing Moon and the Black Cherries Moon — each of which represents various seasonal changes, or maturing crops, and originate from different cultures. 

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Samantha Mathewson joined Space.com as an intern in the summer of 2016. She received a B.A. in Journalism and Environmental Science at the University of New Haven, in Connecticut. Previously, her work has been published in Nature World News. When not writing or reading about science, Samantha enjoys traveling to new places and taking photos! You can follow her on Twitter @Sam_Ashley13.