The Missouri State Highway Patrol said water patrol troopers worked into the night Wednesday, pulling four people from homes and three others from a boat that ran out of gas around the small town of Craig.
"The flooding this year could be worse than anything we've seen in recent years, even worse than the historic floods of 1993 and 2011", she said.
In Niobrara, Nebraska, south of the Missouri River near the border with South Dakota, Mayor Jody Stark said flooding that began on Thursday had devastated his community of 350 people, with businesses being the hardest hit.
Authorities have rescued several people stranded by flooding in northwest Missouri as the swollen Missouri River continues to cause damage and strain levees in several Midwestern states.
Ricketts said that, in terms of how many places have been affected by the flooding, "I don't think there's ever been a disaster this widespread in Nebraska".
Scientists said on Thursday that climate change played a hand in the deadly floods, while a Trump administration official said more study was needed before making that link.
Experts plan a briefing on their flood forecast at the National Water Center in Tuscaloosa, Alabama.
Rapidly melting snow in the upper Midwest is contributing to flooding that will eventually make its way downstream to the Gulf Coast, forecasters have said.
"It's really too early to know for sure how bad this is going to get".
In part of the South, it already is.
The U.S. Army Corps of Engineers said water was also flowing over several other levees, including one near Missouri's Bean Lake.
The swollen river has been flooding some unprotected western MS communities since last month. A local ethanol plant was also shut down amid the flooding.
Residents around Rolling Fork, Mississippi, first noticed water rising from swamps in late February.
The water eventually invaded some homes in that community, about 40 miles (65 kilometers) north of Vicksburg.