Although Colorado saw the bomb cyclone manifest itself in the form of snow, rain is the main culprit in Iowa and IL.
The quickly rising floods evacuated people from their homes, washed out roads in communities, and left farmers anxious all the water would drown livestock.
Around midday, Sioux Falls' precipitation was expected to turn from rain to snow - which has already brought perilous conditions to the western part of the state. The storm brought winds beyond 90 miles per hour and stranded more than 1,100 motorists in blizzard conditions on Colorado highways on Wednesday.
"With the frozen ground and amount of rain our area had, it was just a flawless set of circumstances that led to the flooding we're seeing in Nebraska and Iowa", meteorologist Paul Fajman told the AP.
On Friday, Iowa Governor Kim Reynolds signed an emergency disaster proclamation for funding to combat flooding in parts of the state caused by the "bomb cyclone".
All the scientists agreed that aberrant climate conditions, such as the hurricanes that have ravaged U.S. East Coast and Gulf of Mexico states in recent years, were the results of climate change.
"Just today we're facing blizzards, white-out conditions, flooding, dense fog, and each of those pose a unique risk", he said.
Nebraska, under a state of emergency since Tuesday night, is trying to cope with historic flooding.
Many streams will see moderate to major flooding through the weekend, the service said, and flooding along the Missouri River will continue into next week.
Wednesday's explosive development of a late winter storm over eastern Colorado created rough times for people both on land and in the air.
When a storm drops barometric pressure of at least 24 millibars, units of atmospheric pressure, within 24 hours or less, it bombs out or turns into a bomb cyclone.
Wind, blowing snow and snow-packed roadways also made travel treacherous in western Nebraska.
About 175,000 people are without power, majority in Colorado and Texas.
Daniel Groves, 52, was killed after a wayward 2001 Volvo had struck him while he was on the scene of another vehicle that slid off Interstate 76 in Weld County.
About 50 National Guard soldiers and airmen used specialized vehicles with tank-like treads to rescue 75 people stranded in their cars during the storm.
The window-rattling storm brought blizzards, floods and a tornado across more than 25 states Wednesday, stretching from the northern Rocky Mountains to Texas and beyond.
In parts of Arkansas, Mississippi, Missouri and Tennessee, tornado watches were issued until Thursday afternoon. No deaths or injuries have been reported as yet.
Bria McKenzie, 22, said she and her mother, brother and sister were stuck in their auto for more than two hours on a hilly road in Colorado Springs. Air rushed into the low-pressure area and then rose into the atmosphere, causing severe weather.
"It is a tragic reminder that people's lives are at stake", said Shoshana Lew, head of the Colorado Department of Transportation.