Tornadoes pummeled towns in northern Texas and northeastern Oklahoma on Saturday night as storms across the Great Plains damaged homes, overturned trucks and left nearly 250,000 households without power.

In Texas, a tornado overturned semitrailer trucks and damaged motor homes as well as a marina in northern Denton County, said Dawn Cobb, a county spokeswoman. She added that the number of injuries was not known.

“There has been heavy damage that we can tell,” Justin Stamps, the police chief of Valley View, a city north of Dallas, said in an email, adding that the town was in the early stages of rescue operations.

In Oklahoma, a tornado downed trees and power lines, leaving some roads inaccessible and cutting out electricity, the authorities in Rogers County said on social media. “There is a lot of damage from tonight’s storm,” said the police department in Claremore, a city about 30 miles northeast of Tulsa.

Officials in Oklahoma activated an emergency operations center on Saturday to coordinate efforts statewide in anticipation of the extreme weather, and they advised residents to be ready to take shelter.

A total of nearly 250,000 customers were without power in Arkansas, Kansas, Missouri, Oklahoma and Texas early Sunday morning, according to the site PowerOutage.us.

Many areas of the Great Plains were still bracing for bruising hailstorms, as a weeklong string of severe weather continued through the holiday weekend. More than three million people were under a tornado watch in parts of Arkansas, Kansas, Missouri and Oklahoma early Sunday.

The United States has come under an onslaught of destructive storms in the past week, with at least a few reports of tornadoes each day.

Five people died and part of a city was obliterated in Iowa on Tuesday after the southwestern part of the state was swallowed by a system that produced a powerful tornado that carved a 43-mile path and packed winds of at least 185 miles per hour.