May 2019 Full Moon Tonight Is A Blue Moon

Blue Moon

The Full Moon tonight on on Saturday, May 18, 2019 is a Blue Moon because four moons are occurring within a season.

When is the May 2019 Full Moon?

This Blue Moon begins with a moonrise over the Atlantic Ocean at 8:05 p.m. Eastern Daylight Time on May 18, 2019, which sets the following morning at 7:11 a.m. (with a few minutes of variation depending on your exact location in Florida or several minutes along the rest of the U.S. east coast).

Tonight’s Full Moon will technically be 99.7% full at 5:11 p.m. Eastern Daylight Time.

Where to watch tonight’s Blue Moon:

The Blue Moon can be seen from anywhere on Earth, unless there is local cloud coverage.

How often is a Blue Moon?

Blue Moons occur when there is a second full moon in a calendar month or when a season has four full moons.

Full moons are separated by 29.5 days but seasons are 88 to 92 days long – so it is possible to fit four full moons into a single season. This happens just over two-and-a-half years, on average.

When there are four full moons in a season, the third full moon is considered a Blue Moon.

This is why the phrase “Once in a Blue Moon” is commonly known to mean something rare and offbeat because of the rare occurrence of a Blue Moon.

Is a Blue Moon really blue?

The date of a full moon doesn’t affect the full moon’s color. The Full Moon on Saturday, May 18, 2019, will be pearly-gray to most viewers on Earth, as usual.

According to NASA, the key to a moon appearing blue is to have lots of particles slightly wider than the wavelength of red light (0.7 micron) and no other sizes present in the air. This is rare, but volcanoes sometimes produce such clouds, as do forest fires.

Humans saw blue moons almost every night when the Krakatoa volcano exploded in 1883 with the force of a 100-megaton nuclear bomb. Plumes of ash rose to the very top of Earth’s atmosphere.

Some of those ash-clouds were filled with particles about 1 micron wide – just the right size to strongly scatter red light while allowing other colors to pass. White moonbeams shining through the ash-clouds emerged blue, and sometimes green.

People also saw blue-colored Moons in 1983 after the eruption of the El Chichon volcano in Mexico. And there are reports of blue Moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.

Why is this Full Moon in May named the Flower Moon or Corn-planting Moon?

These full moon names are associated with seasonal occurrences that happen in May. Summer flowers begin to bloom in May which is why it is called a Flower Moon. Corn-planting Moon gets its name from the start of corn planting that happen in May.

Image credit: NASA (blue-enhanced by Brevard Times)