DURHAM, N.C. >> After a rare winter storm walloped the southern United States with record snowfall, the region faced dangerous icy road conditions and a bitter chill Thursday that raised the possibility that some streets may remain impassable until the weekend.

From the swamps of Louisiana to beaches in the Carolinas, the conditions left officials in much of the South delivering a similar message. The effects of the storm were not over, they told residents, and driving remained a hazard on untreated roads still frozen with slippery ice.

While temperatures briefly rose above freezing in parts of Louisiana, southern Alabama and Mississippi, nighttime temperatures plummeted in areas including Georgia, northern Florida and coastal communities in the Carolinas, causing snow and ice to refreeze on roads. Morning commuters faced an increased risk of black ice, the slick patches that can form unpredictably and almost invisibly because they blend in with the asphalt.

“Ice is ice, and it will present a hazard to motorists if they’re not prepared,” said Richard Bann, a meteorologist with the National Weather Service.

That pattern — of ice partially melting, only to refreeze at night — was expected to continue for much of the South until at least Saturday morning.

The threat is worse in a region that is unaccustomed to severely cold weather and where snow plows are not regularly well stocked. Temperatures as low as 12 degrees Fahrenheit were possible Thursday morning in parts of southern Mississippi, Alabama, Georgia and the Florida Panhandle, according to the National Weather Service, which issued an extreme cold warning for the area through midmorning.