Sustainability Environment

South Dakota skies turn green amid severe thunderstorm

The strange phenomenon came right before the area was hit by a derecho.
The sky over Sioux Falls, SD turned bright green on Tuesday shortly before a derecho, a powerful stretch of thunderstorms, hit the city. ( Photo via Twitter/ @jkarmill)

Story at a glance


  • Skies over Sioux Falls, S.D., turned a bright green Tuesday afternoon.

  • The severe weather was a derecho, a powerful storm system that can travel for hundreds of miles and bring heavy rain and powerful winds. 

  • Green skies are not unheard of before a storm, but the exact reason why this happens is still unclear. 

The sky above Sioux Falls, S.D., turned a bright shade of emerald green on Tuesday right before severe weather barreled through the southeastern part of the state.  

Sioux Falls was hit with more than 3 inches of rain over a few hours last night and strong wind gusts as part of a derecho, the Midwest’s answer to a hurricane.  

Derechos are massive thunderstorm bands that can travel hundreds of miles in a relatively straight line and may be just as destructive as a tornado, according to the National Weather Service.  


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Tuesday’s derecho traveled almost 1,150 miles, affecting roughly half a dozen states including Nebraska, Illinois, Iowa, Minnesota and Montana, according to the Mitchell Daily Republic. Winds surpassed 90 mph in places like Huron and Agar, S.D.  

Derechos are relatively rare, but this is the second time South Dakota and its surrounding states have been hit with one this summer. At one point, nearly 30,000 people were left without power, according to USA Today.  

Green skies are not an uncommon phenomenon during severe weather, but the exact reason why it occurs is still unclear, according to AccuWeather. 

But the time of day that thunderstorms occur may play a part in the viridescent skies.  

Severe weather like thunderstorms tend to take place later in the day when the sun is closer to the horizon. As the sun’s position in the sky drops lower, the spectrum of light changes from blue to more red, AccuWeather explains. 

When the light from under thunderclouds, which appears blue due to water droplets, mixes with red sunlight, the resulting color is green.  


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