The floodwater slowly subsided Thursday in parts of Oklahoma and Kansas after killing 12 people, but an approaching storm system could hamper efforts to clean up after weeks of heavy rain damaged homes, businesses and roads.
In Texas, officials were bracing for up to 3 inches (7.6 centimeters) of rain and even more damage.
An estimated 1,000 homes in Texas have already been severely damaged or destroyed by the widespread flooding since late May. The slightest additional rainfall could cause flash flooding where rivers, lakes and reservoirs are already full.
"Unprecedented," said Jack Colley, chief of the Texas Division of Emergency Management. "Mostly this time of year we're fighting wildfires ... The problem with this is, the water won't go away."
The weather already has been blamed for 11 deaths in Texas in the past two weeks. The 12th death was in Missouri, when a 16-year-old girl was killed after she drove her car through a flooded low-water crossing and was swept into a creek. Her body was found Wednesday.
The affected area covers 48,000 square miles (30 million acres) from North Texas to the Rio Grande Valley, a section roughly the size of the state of Mississippi.
But concerns eased Thursday that a full Lake Texoma along the Oklahoma-Texas line would send floodwaters into the Red River.
Floodwater was ebbing in several northeastern Oklahoma communities, but meteorologists predicted more problems because lakes and reservoirs were already full.
The worst flood damage was in Miami, where the Neosho River crested at about 29 feet (8.8 meters), its highest stage since 1951, before beginning its decline.
A shelter set up in the city housed about 55 people, and flood damage was expected to affect about 600 homes, Spurgeon said.
In Kansas, water was receding in the community of Osawatomie as drainage structures were opened on the Pottawatomie River, and power had been restored to about 60 homes, allowing those residents to return, Miami County officials said.
But south-central Kansas was hard hit overnight torrential rains, and at least 1,000 people were out of their homes throughout southeast Kansas, said Sharon Watson, spokeswoman for the Kansas adjutant general.
In northeastern Oklahoma, the Caney River began slowly falling after cresting at 34.18 feet (10.42 meters), according to the National Weather Service. The river, which forced hundreds of residents near Bartlesville from their homes this week, wasn't expected to fall below flood stage until Sunday night, the weather service said.