The sky above an American city turned bright green during intense storms that left thousands without power.
Residents in Sioux Falls in South Dakota experienced the bizarre phenomenon on Tuesday 5 July, shortly before thunderstorms hit the area.
Isaac Longley, a meteorologist at AccuWeather, told the Daily Mail: “While it is relatively common to see these green skies, especially in the Plains, the skies associated with the severe storms that pushed through Sioux Falls during the afternoon of July 5th appeared even greener than normal.
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“This of course caught the attention of many who had never seen skies so green.
“In this particular case, the green skies lasted for around 10-20 minutes as the storms approached the city of Sioux Falls.”
According to the National Weather Service, the green skies were due to a derecho - a fast-moving, intense wind storm that happens alongside thunderstorms.
Explaining what causes the phenomenon, Longley added: “Thunderstorms tend to occur later in the day due to the sun's energy during the day helping to fuel them.
“As many of us know, the sun appears redder later in the day as it approaches the horizon. However, light underneath a tall thundercloud appears blue due to the scattering by water droplets.
“When the blue light is illuminated by the red light from the setting sun, it appears green, which is why some thunderstorms have that greenish hue to it.”
So there you go.
Photographs of the green sky were shared on social media, with Twitter user writing: “Oh my gosh! Look at how green the sky is ahead of severe storms near Sioux Falls, SD!”
Another said: “Have never seen something like that. Green sky with combination of blue in Sioux Falls SD."
While someone else joked: “I told you that Sioux Falls shouldn’t have stolen those ruby slippers…”
Peter Rogers, a meteorologist with the Weather Service’s office in Sioux Fall told The New York Times: “I think it caught a lot of people’s attention because the sky did have that very unique green colour to it.
“Because of the unique colour that it did exhibit, I’m guessing that it will probably be a topic of discussion for quite a long time.”
As well as the skies turning green for around 20 minutes, the area was battered by storms with winds nearing 100mph.
The strong winds left thousands without power, before eventually tapering off at around 5.30pm.
Energy suppliers are currently assessing the damage.
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Claire Reid