ATLANTA (AP) - Forecasters are warning of treacherous holiday travel and life-threatening cold for much of the nation as an arctic air mass blows into the already-frigid southern United States.

“We’re looking at much-below normal temperatures, potentially record-low temperatures leading up to the Christmas holiday,” said Zack Taylor, a meteorologist with the National Weather Service.

The polar air arrives as an earlier storm system gradually winds down in the northeastern U.S. after burying parts of the region under two feet (61 centimeters) of snow. More than 80,000 customers in New England were still without power on Sunday morning, according to poweroutage.us, which tracks outages across the country.

Locally, tonight will be around 19. Tuesday night temperatures are expected to drop to 17. On Thursday, there is a chance of snow in the morning, changing over to rain in the afternoon.

But by Christmas Eve, temperatures will dip again. The daytime high is near 22, with a low at night around 8 degrees.

Christmas Day will be mostly sunny, with a high near 24.

The incoming artic front brings “extreme and prolonged freezing conditions for southern Mississippi and southeast Louisiana,” the National Weather Service in a special weather statement Sunday.

By Thursday night, temperatures will plunge as low as 13 degrees (minus 10.6 Celsius) in Jackson, Mississippi; and around 5 degrees (minus 15 Celsius) in Nashville, Tennessee, the National Weather Service predicts.

For much of the U.S., the winter weather will get worse before it gets better.

The coming week has the potential for “the coldest air of the season” as the strong artic front marches across the eastern two-thirds of the country in the days before Christmas, according to the latest forecasts from the federal Weather Prediction Center in College Park, Maryland.

The center warned of a “massive expanse of frigid temperatures from the Northern Rockies/Northern Plains to the Midwest through the middle of the week, and then reaching the Gulf Coast and much of the Eastern U.S. by Friday and into the weekend.”