At least five people are dead after powerful storms tore through a rural area of Texas, obliterating homes and leaving thousands without power.

Sheriff Ray Sappington said the victims include three family members who were found in one home near Valley View, a rural community near the border with Oklahoma.

The destructive storms began on Saturday night. Officials said a tornado north of Dallas overturned heavy vehicles, shut down an interstate and caused extensive damage to a rest stop on a main road where drivers had rushed to take shelter.

Speaking on Sunday morning, Mr Sappington said: “Search and rescue is ongoing but we’ve already started to do recovery of the deceased. We have five confirmed (dead), but sadly we think that number is probably going to go up.”

Forecasters had issued tornado and severe thunderstorm warnings for parts of Texas and Oklahoma on Saturday, as some heat records were broken during the day in south Texas and residents were warned the high temperatures would continue throughout the long weekend.

A tornado crossed into northern Denton County in Texas late on Saturday and overturned a number of trucks, stopping traffic on Interstate 35.

Denton County community relations director Dawn Cobb said the tornado was confirmed near Valley View, moving east at 40mph, prompting the National Weather Service to issue a tornado warning for the area.

The storm damaged homes, overturned motorhomes and knocked down power lines and trees throughout the area.

The fire service in the city of Denton said emergency personnel were responding to a marina “for multiple victims, some reported trapped”.

In Claremore, Oklahoma, police announced on social media that the city has “shut down” as a result of storm damage, including downed power lines and trees and inaccessible roads.

Excessive heat, especially for May, is the danger in south Texas, where the heat index was forecast to approach 49C in some spots during the weekend. Actual temperatures will be lower, but the humidity will make it feel that much hotter.

Sunday looks like the hottest day with record highs for late May forecast for Austin, Brownsville, Dallas and San Antonio, forecasters said.

Brownsville and Harlingen near the Texas-Mexico border already set new records on Saturday for May 25 – 37C and 38C respectively, according to the weather service.

Wildfire warnings are in place across Texas, New Mexico, Oklahoma, Arizona and Colorado.