Thunderstorm Wind in Dewey County, South Dakota

Brief but intense heavy rainfall from thunderstorms, on top of weeks of wet weather, resulted in additional flooding across Marshall, Hamlin, Codington, and Deuel counties starting on the 17th and persisting well into the 18th. An estimated 3 inches of rain fell in Lake Poinsett, while 1.63 inches was recorded by the COOP sensor 20 miles north northeast of Aberdeen, 1.62 inches was submitted by the CoCoRaHS volunteer in Claremont, and 1.5 inches by the CoCoRaHS observer in Hayti. Flooding was most prominent in urban areas such as Aberdeen where multiple roads and intersections flooded. Clear Lake and Lake Poinsett would also see significant water issues.

These storms would also generate sporadic strong winds, with a gust of 63 mph recorded at the Aberdeen Regional Airport. A 61 mph gust was recorded by the South Dakota Department of Transportation mesonet station 4 miles west of Trail City, and a gust to 62 mph at the South Dakota State University mesonet station near La Plant.