In all, cities across the region, from Minneapolis down to New Orleans, have been slammed by heavy rain and flooding.
And it's not over yet. More heavy rain is in the forecast for today, and over 10 million remain under flood warnings from Oklahoma into Kansas, Missouri and Illinois. The greatest flash flood potential will be from Texas into Arkansas, where 2 to 4 inches of rainfall will be common.
Here's a look at the extent of this flooding across the region.
The hardest hit areas will likely be along the Arkansas River, with a crest today in Tulsa near the record for the river. Floodwaters from the Arkansas River have inundated homes outside Tulsa, such as in these photos from May 23 in Sand Springs.
Debbie Chavez, who has lived with her family in Sand Springs for 24 years, said evacuation started after the water was in the driveway of her neighbors' house last week. She took the below photos of the rising water.
Tulsa Mayor G.T. Bynum warned his city to prepare for the "worst case scenario we've had" in the city's history of flooding.
US Rep. Kevin Hern, who represents parts of Tulsa County and Sand Springs, said he was extremely concerned about the aging levees in his district.
"The devastation from the Arkansas River flooding is real, and the continued risk to citizens and businesses is equally as real," he said.
The Arkansas River, already rising, will reach near-record or record levels -- above 40 feet in some areas -- Thursday afternoon, officials said.