On Saturday, May 18, 2019, at 5:11 p.m. Eastern Time, May’s Flower Moon officially turns full. This particular full Moon is also referred to as a “Blue Moon,” however some may be confused by this name. Most people know that we usually refer to a “Blue Moon” when we have two full Moons in a month (which happens on average every 2 1/2 to 3 years – read more here). There is, however, an alternate definition for a Blue Moon, which is what the Moon on May 18th is.
The Seasonal Blue Moon Definition
Typically, each of the four seasons contains three full Moons. However, sometimes a particular season will have four. When that happens, the third full Moon of that seasonal lunar quartet is designated as a Blue Moon (although no one is sure why the third, and not the fourth, is the one that gets the Blue Moon moniker).
In 2019, spring in the Northern Hemisphere runs from March 20th to June 21st. During that time span of slightly more than three months, these are the full Moon occurrences (in Eastern Time zones):
- Full Worm Moon: March 20, 2019
- Full Pink Moon: April 19, 2019
- Full Flower Moon: May 18, 2019 (Blue Moon)
- Full Strawberry Moon: June 17, 2019
That final full Moon falls before the summer solstice, so it’s not the first full Moon of summer, but rather the fourth full Moon of spring. That makes the May 18th Moon—the third of the four full Moons of spring—a “Blue Moon.” It will also be the last seasonal Blue Moon until August 22, 2021.
And no, it will not be blue in color!