On top of that, rain relief is not coming to everyone. Forecasters warned that with the ground already saturated, even just a small amount of new rain could still have devastating consequences.
"Only an inch or two of rainfall could quickly lead to more flash flooding concerns," the weather service said.
Texas homes wiped away
In Hays County, Texas, just outside of Austin, up to 400 homes have washed away. "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.
More than 1,000 more homes were damaged, and waters washed two main bridges away in Hays.
Thunderstorms could dump 1 to 3 more inches of rain there on Monday -- 5 inches in isolated areas, the weather service said.
And while flood warnings and watches were winding down in most places overnight, a new flood watch loomed from Monday in to early Tuesday for Hays County.
One person was confirmed dead there in the town of San Marcos, and bad weather hindered the search for missing people on Sunday. Rescuers used helicopters to heave stranded residents off the rooftops of buildings surrounded by flood lakes, where normally fields stand.
The Blanco River, which flows through San Marcos, shot past its previous flood record of 33.3 feet to a new one of 40.21 feet late Saturday.
Hours earlier, it ran just over 5 feet deep, according to weather service data. Fortunately, its flood waters should make a rapid retreat.
Nearly 200 miles northeast of Hays County, near Houston, an area of about 400 homes around Louis Creek Dam is under mandatory evacuation. The dam has not breached and workers continue to pack soil on it.
Oklahoma firefighter drowned
In neighboring Oklahoma, two people died.
On Saturday, a woman in Tulsa died after her car hydroplaned. In the nearby town of Claremore, a firefighter got swept into a storm drain while attempting a high-water rescue on Sunday.
There, water levels in creeks normally waste-deep raged up two dozen feet or more over the weekend. Markers signifying moderate to major river flooding dotted the weather map like a measles, particularly along the border with Texas.
The weekend deluges caused Oklahoma City to break its all-time rainfall record for any single month ever. But much of Oklahoma got a rain break on Sunday. Swaths of fog wafted through Tulsa, and on Monday, there is a small chance of thunderstorms there.
A flood watch is on from the southern Plains to the Gulf of Mexico. The heavier rains are moving east, where they are sending some rivers and creeks over their banks -- but nearly as dramatically.
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