Thunderstorms expected to develop in the late afternoon on July 28 could combine to form a derecho over eastern South Dakota, according to the National Weather Service’s Weather Prediction Center.

The last time a derecho hit eastern South Dakota, the sky above Sioux Falls turned green, prompting Reddit users to create images of everything from Cthulhu to the Stay-Puft Marshmallow Man rampaging through the city.

Here’s what happened the last few times derechos have occurred in South Dakota.

July 13, 2024: 100-plus mph wind gusts slam western South Dakota

A cluster of supercells moving southeast out of Montana merged with a line of severe thunderstorms that caused “destructive winds” across much of western and central South Dakota, according to the National Weather Service in Rapid City.

There were widespread wind gusts of 80 mph or more from the border between Montana and South Dakota, and the Missouri River. The strongest gusts of more than 100 mph – including a 108-mph gust near Hoover – were observed in Butte County.

July 5, 2022: A storm turns the sky green over Sioux Falls

A storm that developed over Montana before moved southeast through South Dakota and arrived in Sioux Falls in the mid-afternoon, causing black, blue, grey and green skies above the city.

The strongest reported wind gusts were 99 mph near Howard and 96 mph at the airport in Huron, according to the National Weather Service in Sioux Falls. There were many reports of downed trees and overturned trucks, along with widespread damage to houses, fences and crops.

The storm dropped 3 to 5 inches of rain across the region and left thousands of people without power, the Argus Leader reported at the time. The Great Plains Zoo in Sioux Falls was forced to close temporarily as a result of storm damage.

May 12, 2022: Derecho brings blowing dust, tornadoes to eastern South Dakota

A storm system moved across eastern South Dakota in the late afternoon and early evening, bringing straight-line winds of between 60 and 100 mph, according to the National Weather Service in Aberdeen. A significant amount of blowing dust reduced visibility across southeastern South Dakota as the storm moved through the area.

There were 34 confirmed tornadoes associated with the storm: 19 in Minnesota, 13 in South Dakota and one each in North Dakota and Iowa.

An EF-2 tornado with wind speeds as high as 120 mph tore through Castlewood in Hamlin County, badly damaging a school. A farmstead south of Gary in Deuel County was also devastated by a tornado, the weather service said.

In Sioux Falls, the storm caused about $200,000 worth of damage, the Argus Leader reported.

What is a derecho?

A derecho is a widespread, long-lived wind storm associated with a band of rapidly moving showers or thunderstorms, according to the National Weather Service. A derecho can produce destruction similar to tornadoes, and the term “straight-line wind damage” is sometimes used to describe derecho damage.

“By definition, if the wind damage swath extends more than 240 miles and includes wind gusts of at least 58 mph or greater along most of its length, then the event may be classified as a derecho,” the weather service says.

USA TODAY reporterJohn Bacon contributed to this report.