Hundreds of residents in the northern US states have been ordered to evacuate North and South Dakota, as federal officials step up water releases to relieve pressure on six reservoirs.
Heavy rains coupled with a deep melting snowpack have overwhelmed Missouri River reservoirs from Montana through South Dakota, prompting emergency workers and locals to set up sandbags around residential areas.
Residents in Nebraska, Iowa, and Missouri were also braced for widespread flooding.
One South Dakota resident has moved from his home.
"It's not a home anymore. It's just a house. We moved out about a week ago and went elsewhere," he said.
National Guard troops have also been helping to protect buildings.
"What we're doing is securing the city infrastructure, building up levees where needed," Captain David Larson of the Missouri National Guard, said.
The Missouri River basin forms the northwest section of the Mississippi River system that stretches from the Rocky Mountains to western New York, and funnels water down through Louisiana to the Gulf of Mexico.