The Kansas National Guard was helping with evacuations in Osawatomie, in eastern Kansas, one of the hardest-hit communities in the region.
"It's an extremely unusual amount of rain in a short period of time," Miami County Under-Sheriff Mark Schmidt told CBS News. "That's more rain than we probably get most of the summer."
Meanwhile, more than 42,000 gallons of crude oil spilled into the Verdigris River from the Coffeyville Resources refinery Sunday, Watson said.
The plant was shutting down in response to the flooding when the accident occurred. The plant had been transferring oil from a storage facility to the refinery's main storage tank. Because of an elevation difference between the two tanks, the oil continued to flow and caused the main tank to overflow, she said.
"We're asking everyone to avoid the floodwaters (in the Coffeyville area)," Watson said.
Maj. Gen. Tod Bunting, the state adjutant, said the oil was expected to flow from the Verdigris to the Neosho River and eventually end up in Grand Lake, Okla.
"The water's moving too fast for us to do anything with it right now," Bunting said Monday morning.
In Osawatomie, Mayor Philip Dudley kept an eye on Pottawatomie Creek on the town's south flank and the Marais des Cygnes on the north.
"I think the Marais des Cygnes will be OK," Dudley said. "I'm still concerned about Pottawatomie Creek. It's supposed to get over 49 feet on Monday."
The levees and dikes in Osawatomie held, after reinforcement work by volunteers with sandbags, but rainwater pooling in low-lying areas overwhelmed pumps and flooded neighborhoods on both sides of town.
About 40 percent of the town's 4,600 residents were ordered to leave when areas near two rivers flooded.
"Any time you're evacuated from your home and don't know when you're going to be able to get back, it's upsetting," Schmidt said. "A lot of the homes, it's generation after generation of people living there and it's quite unnerving."
Retired welder Claude Blackmon, 65, was able to save his lawnmower, guns and some important papers from his mobile home, where he lived for two years after his wife died. The rest of his belongings, including new appliances and family heirlooms, were inundated in water that nearly covered the trailer. None of it was insured, he said.
"I don't know what I'm going to do," he said. "I'm a little too old to start over now."
Storms have claimed 11 lives in northern and central Texas in the past two weeks. Authorities were still searching for two 20-year-old men from Leander whose Jeep Cherokee was found submerged in a creek Thursday.
President Bush declared Texas a major disaster area Friday, ordering federal aid for Cooke, Coryell, Denton, Grayson, Lampasas and Tarrant counties.
Gov. Rick Perry declared disaster areas in 37 counties across Texas. Residents of those counties would have access to state assistance programs.
The weather service measured more than 11 inches of rain in June at Dallas-Fort Worth International Airport, about a half-inch shy of the 1928 record.
The normal rainfall is about 4 inches, reports CBS News meteorologist George Cullen.
The storms resulted in 152 flight cancellations and 56 diversions Sunday, while other travelers experienced flight delays of about one hour, airport spokesman David Magana said.
At least 200 people have been displaced from their homes near the Brazos River in Texas' Parker County. Some houses sustained minimal damage, while up to 4 feet of water had seeped into others.
Some of the worst flooding Sunday in Oklahoma was near Bartlesville, where the Caney River was more than three feet above flood stage.
Amtrak's Heartland Flyer passenger rail system between Oklahoma City and Fort Worth was halted Sunday because of flooding in north Texas, and passengers were bussed instead, said Terry Angier, a spokeswoman for the Oklahoma Department of Transportation.
In north Texas, hundreds of residents near the overflowing Wichita and Brazos rivers remained evacuated Sunday.
The Brazos River was expected to crest early Monday before falling below flood stage during the day, Kertok said.
About 100 miles north in Wichita Falls, officials were concerned about contaminants in the water, making them unsure of when they could let some residents return after urging them to leave Friday. Those exposed to floodwater were urged to get tetanus vaccinations, said Barry Levy, a Wichita Falls spokesman.
If the water rises any more James Turner's house could be next.
"No, I'm not staying here. I've already got a place to stay and everything like that," Turner told CBS News correspondent Hari Sreenivasan. "I'm not going to wait until the water comes and gets me. I'm outta here."
Across town, Norman Herzhold is staying put, even without power and with water at his doorstep.
"I've got to keep the generator going — got a deep-freeze full of food and a refrigerator full of food and, you know, this is just an inconvenience," Herzhold said.
Kansas Gov. Kathleen Sebelius on Sunday added six more counties to her declaration of a state of emergency, including Allen, Cherokee, Elk, Franklin, Greenwood and Miami, and said she planned to survey the damage Monday.
"It's going to be a few days before we get some of the higher rivers to come down," said Maren Stoflet, a National Weather Service meteorologist in Pleasant Hill, Missouri.
The Verdigris River at Independence set a new record of 52.4 feet Sunday morning, shattering the old mark of 47.6 feet and more than 20 feet above flood stage.