A grandmother and four of her grandchildren were killed and another person also died in floods in Texas caused by storms that unleashed tornadoes, damaging hail and torrential rains on several central U.S. states, officials said on Saturday.

The woman and her grandchildren died in Palestine, Texas, 160 km southeast of Dallas, after escaping a house where flood waters had reached the roof line. They were then swept away, Palestine police Captain James Muniz said.

"They were able to get out but they were washed away," he said, adding their bodies were recovered on Saturday.

Those killed were identified as Jamonicka Johnson, 6, Von Johnson Jr., 7, Devonte Asberry, 8, Venetia Asberry, 9, and Lenda Asberry, 64, the city said. Palestine police took the bodies to Tyler, Texas, for autopsies, officials said.

A Palestine man, Giovani Olivas, 30, was swept under flood waters around Anderson County Road 370. His body was found late on Saturday afternoon, according to Anderson County Sheriff Greg Taylor.

Seven homes were evacuated and temporary shelters were established, officials said. The city received 19 cm of rain in less than an hour, which caused the floods.

"I don't recall ever seeing this much water rise so fast and in such a short period of time," Palestine Mayor Bob Herrington said in a statement, wherein he also offered condolences to the family of the five victims.

The National Weather Service issued a flash flood watch extending from east Texas into much of Mississippi and a severe thunderstorm watch for New Orleans and the southern Louisiana region.

"Strong to severe thunderstorms are expected today into this evening across the lower Mississippi Valley, Tennessee Valley, Ozarks and the Ohio Valley," it said.

Strong winds in the Houston area downed trees and cut power lines, the service said. As of 10:30 a.m. local time, more than 4,200 customers in the region were without power, CenterPoint Energy reported.

There were seven reported tornadoes from the storm system on Friday in Texas and Oklahoma, it said. A twister caused damage to several structures and ripped through mobile homes in Ninnekah, about 80 km southwest of Oklahoma City, local news reports said.