"Predictions from the National Weather Service indicate that significant flooding along the Wichita River is very likely," the town's emergency management agency said. "
"We do have whole streets that have maybe one or two houses left on them, and the rest are just slabs," said Kharley Smith, emergency management coordinator in Hays County, Texas.
Crews are still surveying damage, she told reporters Sunday; between 350 and 400 homes in the Texas county are gone, and more than 1,000 were damaged. Two main bridges washed away, she said, and other sustained major structural damage.
In San Marcos, Texas, a city between San Antonio and Austin that was among the hardest hit areas, Fire Marshal Ken Bell said at least one person was confirmed dead. Crews are searching for three missing people, he said, and others are trapped in areas that authorities can't reach because bad weather has forced them to stop air rescues.
It was not immediately clear whether the fatality was one of the people reported missing. Authorities don't yet know how devastating the damage is, and they're bracing for the possibility that more rainfall could send floodwaters surging back into the city, he said.
"Right now is not the time to return to your homes," Bell said Sunday after the severe weather forced the evacuation of hundreds of residents.
"We have infrastructure damage throughout the entire county (of Hays)" he said. "There are power lines down, debris in the roadways, bridges undermined -- this is not the time to start moving."
It was a warning other authorities in the region echoed after rainfall broke records and river banks in northern Texas and Oklahoma overnight.
At least two people died in storms that hit Oklahoma. On Saturday, a 33-year-old woman in Tulsa died after her car hydroplaned, said Keli Cain, the state's emergency management spokeswoman.
Nearby in the town of Claremore early Sunday, a firefighter died attempting a high-water rescue as emergency crews scrambled to pull residents from floodwaters.
With more rain falling, the torrents have already pushed Oklahoma City handily past a rain record, and rescuers have carried out at least 48 high-water rescues.
More than 1,000 in shelters
In Hays County, Texas, adjacent to Austin, hundreds of people were rescued or evacuated from their homes, according to sheriff's office spokeswoman Lt. Jeri Skrocki.
Authorities had to open more evacuation centers because the first one filled up so quickly.
More than 1,000 people were in shelters Sunday afternoon, Smith said.
Despite the heavy rain, western Oklahoma and parts of the Texas Panhandle and central Texas are still facing moderate drought or abnormally dry conditions, according to the U.S. Drought Monitor. The rainfall should put a dent in it, though.