South Dakota sky turns green. See the strange weather phenomenon in photos.

·3 min read

SIOUX FALLS, S.D. – Before severe weather swept through South Dakota on Tuesday, residents around Sioux Falls witnessed a hauntingly rare phenomenon: a green sky.

Yes, the sky was green. And not a light green – the green that's the color of the sky before aliens arrive in a sci-fi movie. Or before the Wicked Witch of the West threatens Dorothy and her little dog, too.

The National Weather Service confirmed that a derecho barreled through much of South Dakota – as well as Minnesota and Iowa – on Tuesday, leaving thousands without power for hours after the "destructive," long-lasting wind storm. As of Tuesday night, the extent of the damage from the storm was unclear as the storm and warnings stretched as far as Wisconsin, the weather service said.

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In addition to heavy rain, the storm brought black, blue, gray and, again, murky green skies around southeastern South Dakota, including the Sioux Falls area. Weather watchers took to Twitter to share photos of the ominous sky while we tried to find out what the green sky means.

Do green skies mean a tornado is on the way?

Green skies often come with severe weather, but that does not mean a tornado is coming. There isn’t a direct correlation between the two, according to AccuWeather.

Why is the sky green in bad weather?

It’s not fully understood why green skies occur, the Scientific American reports. But if a thunderstorm occurs during a time of red light, like a sunset, water particles in the air can make it appear as if the sky is slightly green in color, some researchers say. The gray cloud of a thunderstorm, water particles that bend red light to appear blue and ample red light in the sky can create the perfect storm for a green sky.

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See the green sky photos in South Dakota

User Jaden (@jkarmill) caught the sky looking something akin to neon green.

A meteorologist on Twitter posted a photo of the green sky and a graphic explaining the phenomenon.

In this video, one person compares the sky to those seen in "The Wizard of Oz," the other to "Stranger Things." (Warning: There is a cuss word.)

Even a meteorologist from Virginia took notice of how green the Sioux Falls skies turned.

Of course, a Sioux Falls weather reporter took notice.

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Follow Cecelia Hanley on Twitter @CHanley_Digital.

Contributing: Alfonzo Galvan, Dominik Dausch and Shelly Conlon, Sioux Falls Argus Leader; Wyatte Grantham-Philips, USA TODAY

This article originally appeared on Sioux Falls Argus Leader: South Dakota skies turn green before severe weather, derecho hits