Does a ‘blue moon’ actually exist?

Here’s when astronomers say you can spot a blue moon

To make Halloween this year seem just a little more Halloween-y, some will be celebrating and possibility trick or treating under the light of a blue moon.

Most people have heard the phrase, “once in a blue moon” when referring to something that doesn’t happen very often.

But an actual blue moon is traditionally defined as the second full moon to happen in a single calendar month, and usually doesn’t have anything to do with the actual color of the moon.

In this case, our second full moon, and now blue moon, will be on Halloween night.

The first one happened during the first week of this month.

Sometimes, though, a blue moon can also refer to the third of four full moons in a single season.

According to, that will happen next in the year 2048, when a monthly blue moon falls on Jan. 31, and a seasonal blue moon on Aug. 23.

So while having nothing to do with the actual color blue, astronomers say there is still a possibility to see a blue-colored moon in your lifetime.

There are situations in which particles in the earth’s atmosphere, like dust or smoke, can bend the light the moon is reflecting to us here on earth.

Scientists say those particles of a certain size can scatter out the red light that we see, creating what appears to be a blue-colored moon.

Because of the same phenomenon, you can also see red or orange moons as well.

If you’re wondering, the next seasonal blue moon will be August 22, 2021.

About the Authors:

Stephanie Serna is a weekday anchor on Good Morning San Antonio and GMSA at 9 a.m. She joined the KSAT 12 News team in November 2009 as a general assignments reporter.