Three Texas siblings who perished in an icy pond were among several dozen deaths in U.S. states gripped by frigid cold Tuesday as crews scrambled to repair hundreds of thousands of power outages in the shivering South and forecasters warned the winter weather is expected to get worse.

Brutal cold lingered in the wake of a massive storm that dumped deep snow across more than 1,300 miles from Arkansas to New England and left parts of the South coated in treacherous ice.

Freezing temperatures hovered Tuesday as far south as Tennessee, Arkansas and North Carolina, and were forecast to plunge again overnight. Parts of northern Florida were expected to sink to 25 F (minus 3.9 C) late Tuesday into early Wednesday.

The U.S. aviation system was returning to normal after a brutal weekend that saw more than 17,000 commercial flights canceled. There were 7,000 cancellations Monday and about 2,800 Tuesday, according to FlightAware, a flight tracking and data company. Less than 400 were anticipated to be canceled Wednesday.

The arctic misery over the eastern half of the U.S. was expected to worsen Friday and Saturday. The National Weather Service said another winter storm could hit parts of the East Coast this weekend, and more record lows were forecast as far south as Florida.

“This could be the coldest temperature seen in several years for some places and the longest duration of cold in several decades,” the agency’s Weather Prediction Center warned Tuesday.

Officials in states afflicted with severe cold reported at least 45 deaths.

Three brothers ages 6, 8 and 9 died Monday after falling through ice on a private pond near Bonham, Texas, Fannin County Sheriff Cody Shook said Tuesday. The boys’ mother said she ran into the freezing lake and frantically tried to pull her sons from the water, but the ice kept breaking beneath them.

In New York City, officials said 10 people had been found dead outdoors in the cold. More deaths were reported across a dozen states.