As another fierce cold front prepares to sweep through the U.S. South on Friday, residents in parts of Mississippi and Tennessee are bracing for a heightened risk of hypothermia. Many have been stranded at home without power for nearly six days in subfreezing conditions, increasing their vulnerability to the cold.

“Prolonged exposure to the cold is particularly dangerous,” warns Dr. Hans House, an emergency medicine professor at the University of Iowa. He notes that while the human body can endure cold temperatures for brief periods, extended exposure can have dire consequences.

The National Weather Service predicts that the incoming arctic air will send temperatures in Southeast cities like Nashville plunging into the teens, around minus 10 degrees Celsius, by Friday night. In Nashville alone, over 79,000 homes and businesses remain without electricity following a massive winter storm that blanketed the eastern U.S. with snow and ice.

Dr. Zheng Ben Ma, the medical director at the University of Washington Medical Center’s northwest emergency department, highlights that the most vulnerable populations—such as the elderly, infants, and those with pre-existing health conditions—may have begun experiencing symptoms of hypothermia within hours of exposure. These symptoms can range from exhaustion and slurred speech to memory loss.

As the situation drags on, Dr. Ma cautions that even younger, generally healthy individuals might start to show signs of hypothermia. The extended duration without power has pushed the crisis to a critical juncture, affecting a broader swath of the population.

“Once you get into days six, seven, upwards of 10, then even a healthy, resilient person will be more predisposed to experiencing some of those deleterious effects of the cold temperature,” he said.

Hundreds of National Guard troops mobilized Thursday in Mississippi and Tennessee to clear debris and assist people stranded in cars or stuck at homes.

Mississippi Gov. Tate Reeves said Guard troops were delivering meals, blankets and other supplies by truck and helicopter. And in Tennessee, Gov. Bill Lee said crews had distributed more than 600 units of warming supplies and over 2,200 gallons (8,328 liters) of gas and diesel.

Nashville Mayor Freddie O’Connell said that they have the most line workers, crews and vegetation support workers in the city utility’s history as they work to get electricity back for everyone.

But the exact timeline for power to be restored, especially in more rural areas, remains unclear.

At least 85 people have died in areas affected by bitter cold from Texas to New Jersey. Roughly half the deaths were reported in Tennessee, Mississippi and Louisiana. While some deaths have been attributed to hypothermia, others are suspected to be related to carbon monoxide exposure.

Dr. Abhi Mehrotra, an emergency medicine physician with the University of North Carolina at Chapel Hill, said it’s important to make sure heat sources used indoors, including generators, are not emitting carbon monoxide, which could be deadly.

More than 230,000 homes and businesses were without electricity Thursday night, according to the outage tracking website poweroutage.us. The vast majority were in Mississippi and Tennessee, with roughly 87,000 each.

Mississippi officials say it’s the state’s worst winter storm since 1994. About 80 warming centers were opened across the state, known as one of the nation’s poorest.

Forecasters say the subfreezing weather will persist in the eastern U.S. into February and there’s high chance of heavy snow in the Carolinas, Virginia and northeast Georgia this weekend, possibly up to a foot (30 centimeters) in parts of North Carolina. Snow is also possible along the East Coast from Maryland to Maine.

The National Weather Service said there was a chance of freezing rain Thursday night in parts of Mississippi, and light snow showers could hit Nashville overnight Friday. Forecasters said the extreme cold and subzero wind chills (minus 18 C) represented the greatest danger.

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