Death toll from the floods and storms reached to 18 in the US as search and rescue teams continue looking for more than a dozen missing people.
Texas suffered the most from the disaster as 11 people died in the lone star state, four in the city of Houston where roads flooded, bridged swept and homes destroyed.
"A lot of folks drove their car into high water and had to abandon those vehicles," Houston Mayor Annise Parker said on Tuesday.
In Oklahoma, six people died as a result of storms and floods since Memorial Day weekend started.
Texas Governor Greg Abbott declared state of emergency in 40 counties saying: “This is the biggest flood this area of Texas has ever seen.”
"It's devastating to see what I saw on the Blanco River when this tidal wave of water just swept away neighbourhoods," he said, reminding flooding that swept more than 40 people who are still unaccounted for.
Heavy rain raised the level of water in Blanco River to 13 metres (44 feet) sweeping and destroying buildings and homes around it, breaking the record of 10 metres (32 feet) from 1926.
“It was literally a large wall of water that came down the Blanco River and destroyed everything in its path,” Hays County Commissioner Will Conley said describing the disaster.
Authorities say they expect the death toll to rise as the missing includes two families from a vacation home that was swept off its foundation.
Thousands of homes were destroyed or damaged as tens of thousands of people had to be carried to safety by rescue teams in Texas and Oklahoma.
In Houston only, the number of seriously damaged homes could reach to 4,000, NBC News reports citing officials.
Extreme weather conditions also affected transportation as more than 200 flights had been cancelled at Houston and Dallas airports by early on Tuesday and flooded roads barred people from going to their businesses.
About 100,000 people experienced power cuts throughout Texas due to storms and rising waters that caused power poles to snap.
The National Weather Service warned for more tornadoes and thunderstorms for later Tuesday, and rains are expected to continue in Texas and Oklahoma this week.