More than 200 million people in US are at risk for some kind of flooding in the coming weeks, forecasters say.

The stage is set for unprecedented major flooding this spring for most of the nation, US weather officials said on Thursday.

More than 200 million people in the United States are at risk of some kind of flooding, with 13 million of them at risk of major inundation, the National Oceanic and Atmospheric Administration said in its spring weather outlook. About 41 million people are at risk of moderate flooding.

The major flooding now occurring in Nebraska, Iowa, South Dakota, Missouri and other Midwestern states is a preview of an all-too-wet and dangerous spring, said Mary Erickson, deputy director of the National Weather Service.

“In fact, we expect the flooding to get worse and more widespread,” Erickson said. This year’s flooding “could be worse than anything we’ve seen in recent years, even worse than the historic floods of 1993 and 2011,” she said.

Those floods caused billions of dollars in damage, and officials said this year’s damage in Nebraska, Iowa and South Dakota has already passed the billion-dollar mark.

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Flooding from a storm last week has already caused nearly $1.5bn in damage in Nebraska alone and killed at least four people with another missing.

Extensive road damage following flooding in north-central and northeastern Nebraska [Handout: State Patrol/Reuters]

Forecasters said the biggest risks include all three Mississippi River basins, the Red River of the North, the Great Lakes, plus the basins of the eastern Missouri River, lower Ohio River, lower Cumberland River and the Tennessee River.

“This is the broadest expanse of area in the United States that we’ve projected with an elevated risk that I can remember,” said Thomas Graziano, a 20-year weather service veteran and director of the Office of Water Prediction. “Is this the perfect storm? I don’t know.”

A lot depends on how much rain falls in the next couple of months, Graziano said, but forecasters say it will be more than average.

The Missouri River has already set records with historic flood marks measured in 30 places in Nebraska, Iowa and South Dakota, Kansas City, forecaster Kevin Lao said.

A flooded parcel of land along the Platte River is pictured in this aerial photograph at La Platte, south of Omaha, Nebraska [Drone Base/ Reuters]

Flooding in the South

Major flooding is already occurring this week on the Mississippi River near several Southern cities including Arkansas City, Arkansas; Natchez, Mississippi and Baton Rouge, Louisiana, according to river gauges and data from NOAA.

The swollen river has been flooding some unprotected western Mississippi communities since last month.

One Mississippi region protected by levees is also flooding. The smaller rivers there cannot drain into the Mississippi River as normal, because a floodgate that protects the region from even worse flooding by the big river has been closed since February 15.

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 (65km) north of Vicksburg.

It’s too early for scientists to make the complex calculations to see if human-caused climate change played a role in the flooding. However, scientists said the conditions are consistent with what they expect from global warming.