It takes a severe atmospheric phenomenon to make a moon blue. But it does happen, upon occasion. It's rarer than a blue moon, in fact.

Video: Blue Moon in July, a Rare but White Sight


A good number of us, at least on Turtle Island, will be deep into Snoozeville when the moon becomes full in the early-morning hours of Friday July 31.

But this one is special and occurs, well, just once in a blue moon. It is of course an actual blue moon—though not in color. Time was when blue moon merely meant “rare, seldom, even absurd,” says NASA by way of explanation. “This year it means ‘the end of July.’ ”

Back in Shakespeare's day, the term had zero astronomical meaning, NASA goes on to explain.

“Since then, however, its meaning has shifted,” NASA says.

These days, blue moon refers to the second full moon in a month. The first one in July was on the second, and the last one falls on Friday July 31.

The timing of this month’s second full moon—the exact moment of fullness is 6:43 a.m. EDT—means that Mother Earth’s satellite will appear blazingly full on the nights of both July 30 and 31, according to And it is indeed fairly rare, if you go purely by the two-per-month definition.

“It’s the first blue moon in the Americas since August 2012; it won’t happen again until January 2018,” tells us.

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That fits, of course, with the moon’s moniker, which stems from a complex series of this-is-how-rumors-get-started misinterpretations that have evolved into what NASA now terms “modern folklore.”

But just like that relationship status made popular by Facebook, it’s complicated.

“In recent years, people have been using the name blue moon for the second of two full moons in a single calendar month,” says “An older definition of blue moon is that it’s the third of four full moons in a single season. Someday, you might see an actual blue-colored moon. The term once in a blue moon used to mean something rare. Now that the rules for naming blue moons include several different possibilities, blue moons are pretty common!” uses the older definition, calling the July 31 full moon blue because it is one of 13 in the 12-month year—an “extra,” if you will.

Regardless, don’t let the nomenclature fool you. The moon won’t change color unless we’re subject to a massive volcanic eruption, or some other major atmospheric disturbance.

“Most Blue Moons look pale gray and white, just like the moon you've seen on any other night,” NASA says. “Squeezing a second full moon into a calendar month doesn't change its color.”

So don’t ignore the blazing white luminescent orb ruling the sky on those two nights, rising in the east-southeast at 7:28 p.m. on the 30th and 8:14 p.m. on the 31st, tells us. It is what you’re looking for.

NASA explains the evolution of the term blue moon, and demonstrates what would have to happen to make it actually turn blue, in detail below. While you're moon watching, note that it's also a fine time to take a swig of Blue Moon beer, whose parent company is celebrating the brand’s 20th birthday this weekend, as points out.

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