A line of storms stretching from the Gulf of Mexico to the Great Lakes has dumped record rainfall on parts of the US Plains and Midwest, causing major flooding that forced at least 2,000 Texans from their homes.
Three deaths were blamed on the storms during Saturday and Sunday, including two in Oklahoma and one in Texas.
One man's body was recovered from a flooded area along the Blanco River in Texas, which rose 26ft in an hour and created huge piles of debris.
The line of storms prompted tornado warnings and watches as far north as Illinois on Sunday night, and the weather system is expected to linger over a large swathe of the region on Monday, dampening Memorial Day holiday plans for many.
Among the worst-affected communities were Wimberley and San Marcos, which are in Central Texas along the Blanco River in the increasingly popular corridor between Austin and San Antonio.
"It looks pretty bad out there," Hays County emergency management coordinator Kharley Smith said of Wimberley, where an estimated 350 to 400 homes were destroyed and where three people remained missing late on Sunday.
"We do have whole streets with maybe one or two houses left on them and the rest are just slabs."
Kristi Wyatt, a spokeswoman for San Marcos, said about 1,000 homes were damaged throughout Hays County, which includes Wimberley and which will be toured Monday by Governor Greg Abbott.
Five San Marcos police cars were washed away and the fire station was flooded. The city imposed a 9pm emergency curfew on Sunday night.
Rivers swelled so quickly that whole communities awoke Sunday surrounded by water. The Blanco crested above 40ft - more than triple its flood stage of 13ft - swamping Interstate 35 and forcing parts of the busy north-south highway to close. Rescuers used pontoon boats and a helicopter to pull people out.
Hundreds of trees along the Blanco were uprooted or snapped, and they collected in piles of debris that soared 20 feet high.
"We've got trees in the rafters," said Cherri Maley, the property manager of a house whose entire rear portion had collapsed with the flooding, carrying away furniture.
"We had the refrigerator in a tree," she said. "I think it's a total loss."
About 1,000 residents were evacuated from roughly 400 homes near an earthen dam at Lake Lewis, about 50 miles north of Houston. Montgomery County emergency management officials fear the dam could fail due to the flooding.
Agency spokeswoman Miranda Hahs said it was not clear when residents would be allowed to return home.
A tornado briefly touched down on Sunday in Houston, damaging rooftops, toppling trees, blowing out windows and sending at least two people to a hospital. Fire officials said 10 apartments were heavily damaged and 40 others sustained lesser damage.
Dallas faced severe flooding from the Trinity River, which was expected to crest near 40ft on Monday and lap at the foundations of an industrial park. The Red and Wichita rivers also rose far above flood stage.
In Colorado, a mandatory evacuation notice was issued on Sunday for residents in the north-eastern city of Sterling, and several counties planned to ask the governor for a disaster declaration.
Meanwhile, tornado warnings and watches were issued on Sunday night for parts of several states, including Kansas, Missouri, Iowa and Illinois.
In north-east Oklahoma late on Saturday, Claremore fire Capt Jason Farley was helping rescue people from flooding when he was swept into a drainage ditch.
His body was recovered an hour and a half later, his chief said. Meanwhile, a state emergency management official said a 33-year-old woman died in a weather-related traffic crash on Saturday.
This May is already the wettest on record for several Plains cities, with days still to go and more rain on the way. Oklahoma City set a new monthly rainfall record this weekend - 18.2in through Saturday, destroying the previous peak of 14.5in in 2013.
S o far this year, Oklahoma City has seen 27.37in of rain. Only 4.29in was recorded overall last year.
Forrest Mitchell, a meteorologist at the weather service's office in Norman, Oklahoma, said it looks like the recent rainfall may officially end the drought that has gripped the region for years, noting that many lakes and reservoirs are full.