The sky above Sioux Falls, South Dakota, turned a spectacular emerald green on Tuesday, just before extreme storms swept through the state’s southern region.
Last night, Sioux Falls saw more than three inches of rain and heavy wind gusts due to a derecho, the Midwest’s equivalent of a hurricane.
Hurricanes do not occur in the Midwest or Plains states. Instead, they experience derechos, which are massive thunderstorm complexes with the impact of a 100-mile-wide tornado that can traverse hundreds of miles and encompass many states. They can be just as destructive as tornadoes.
According to the Washington Post, Tuesday’s derecho went about 1,150 miles, affecting a half-dozen states, including Nebraska, Illinois, Iowa, Minnesota, and Montana. Winds gusted to more than 90 mph near Huron and Agar, SD.
Derechos are uncommon, but this is the second time South Dakota and its neighboring states have been slammed with one this summer, with up to 30,000 people without power at one point, according to USA Today.
Hundreds of people took to social media before, during, and after the storms to reflect on how strange the sky scene looked as the storms hit. Among them were dozens of seasoned storm chasers, many of whom had never seen a sky that color before.
The green sky associated with some severe thunderstorms is due to what the thunderstorm carries – water and a lot of it. Large raindrops and hail are thought to disperse all but blue wavelengths, mainly allowing blue light to penetrate through and beneath the storm cloud.
The sinking sun already skews the light red/yellow in the late afternoon and evening. Green is produced by combining yellow and blue light, but experts in atmospheric optics are still skeptical of the overall procedure.