The National Weather Service also says a derecho classification applies “if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length”.
In South Dakota, residents there have grown used to derechos having recently experienced two such storms. However, the green sky was a highly unusual sight and drew far more people’s attention, with some posting images online.
One person posted: “Green Sky’s all of the sudden in South Dakota USA …”
\u201cGreen Sky\u2019s all of the sudden in South Dakota USA \u2026\u201d
— \u26a1\ufe0fhamaryah Ban Yahawadah \ud802\udd14\ud802\udd0c\ud802\udd13\ud802\udd09\ud802\udd04 (@\u26a1\ufe0fhamaryah Ban Yahawadah \ud802\udd14\ud802\udd0c\ud802\udd13\ud802\udd09\ud802\udd04)
A meteorologist wrote: “Oh my gosh! Look at how green the sky is ahead of severe storms near Sioux Falls, SD!”
\u201cOh my gosh! Look at how green the sky is ahead of severe storms near Sioux Falls, SD! #sdwx\u201d