By Brian Lada AccuWeather meteorologist and employee author
sixteenth May 2019, 09:55:15 EDT
An unusual full moon will fill the sky on Saturday night – a kind of moon that will not open again until 2021.  Many people know the term "blue moon" and know it as the second full moon in a calendar month. However, there is another way for a full moon to earn that familiar nickname.
A passenger plane from American Airlines in Miami crosses Whittier, California, on its way to Los Angeles Airport, Friday, July 31, 2015. (AP Photo / Nick Ut)  "One season – Winter, Spring, Autumn, Summer – usually has three full moons. If a season has four full moons, the third full moon of the season can be called the Blue Moon, "the old farmer's almanac explained on his website.
The full moon of this weekend will be the third of four this spring, making it a blue moon. The first full moon of spring fell on March 20, 2019 at 21:43. EDT, less than four hours after the official start of spring.
Seasonal blue moons are not particularly rare and occur every two or three years. The next seasonal blue moon falls on 22 August 2021.
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Many people in the US who step outside on Saturday night may be looking at a cloud-filled sky and not the blue moon.
A strong system in the central US will spread clouds across most of the region, stretching from the Gulf Coast to the Western Great Lakes and west to the Rocky Mountains.
In the meantime, a storm moving from the Pacific Ocean to the west of the US is spreading clouds across most of the US disturbing seeing in parts of the Mid-Atlantic and the deep South.
The full moon of this weekend can be described as a few other nicknames besides a Blue Moon.
"The May full moon was a time of increasing fertility with temperatures warm enough to safely give birth to young, late frosts and flowering plants," said the old farmer's almanac.
For this reason, the full moon in May is known as Bunny Moon, Flower Moon, Milk Moon and Bud Moon.
Despite its nickname, the moon of Saturday night appears all year round like other full moons.
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