Sioux Falls, South Dakota – Thunderstorms dumped as much as 4 inches of rain overnight across parts of southeast South Dakota, triggering flash flooding that is expected to continue through at least 4 a.m. Thursday.
According to the National Weather Service in Sioux Falls, radar indicated an additional 0.2 to 1 inch of rain could fall in the warning area, which includes Union, Lincoln, Turner, Clay, and Sioux counties in South Dakota, as well as adjacent areas in northwest Iowa and northeast Nebraska. The rainfall rate remains high—between 0.5 and 1 inch per hour—raising concerns for creeks, roads, and low-lying neighborhoods.
Flash flooding is either ongoing or imminent in towns like Vermillion, Elk Point, Akron, and Hawarden. U.S. Highways 77 and 18, as well as local county roads, could become dangerous or impassable overnight. Residents in flood-prone zones are urged to stay off the roads and avoid walking or driving through water.
This is the same region impacted by repeated summer rain events, saturating soils and overwhelming drainage. Urban areas and farmland are especially vulnerable in the early hours.
Flood warnings remain in effect until 4 a.m., but more rainfall or future storms could extend alerts. Drivers should remain cautious through sunrise.
