ATLANTA — Small armies of utility workers labored to turn the lights — and the heat — back on for hundreds of thousands of Southerners as a winter storm that left them without power threatened major cities further up the East Coast.

The Deep South remained a world of ice-laden trees and driveways early Thursday after several unusual days of sleet and snow brought by a powerful system that could bring more than a foot of snow to such metropolises as Philadelphia, Washington and Boston.

At least 12 deaths across the South have been blamed on the stormy weather and nearly 3,300 flights nationwide were canceled with another day of complicated air and road travel ahead Thursday, particularly in the Northeast.

Drivers in and around Raleigh, N.C., became snarled Wednesday in huge traffic jams and abandoned cars in scenes reminiscent of motorist woes in Atlanta during a storm two weeks earlier. In Atlanta, many streets were eerily quiet this storm, with drivers heeding dire warnings to stay off the roads. State troopers say they worked more than 200 crashes in Georgia. Snow was forecast to stop falling and temperatures to rise in most of the state by late morning, but ice remained a concern, with refreezing possible overnight and into Friday.

For some on slick, snow-covered interstates in North Carolina, commutes that should take minutes lasted hours after many got on the highways just as soon as snow and sleet began at midday.

And in South Carolina, more accustomed to occasional hurricanes, some could only relate the damage from ice-snapped tree limbs to that of bygone Hurricane Hugo. Even normally balmy Myrtle Beach, where millions of visitors cavort each summer, cars were coated in thick ice that also frosted palm trees and kiddie rides by the shore.

“I hate driving on this,” grumbled South Carolina resident Mindy Taylor, 43, on her way for rock salt, kitty litter or anything else to melt the ice. “Hopefully it’ll warm up by the weekend and it will all melt. I’m ready for Spring.”

In Alabama, forecasters gleefully spoke of weekend temperatures reaching the 60s after inches of snow or sleet in its northern parts.

The snow, sleet and freezing rain that iced Southern highways also knocked out electricity to more than half a million homes and business as it advanced Thursday up the Interstate 95 corridor to the winter-weary Mid-Atlantic states.

Some Southerners who two weeks ago reveled in the so-called “snow jam” sounded tired this time of sleet and ice encasing highways, trees and even the tombstones of a cemetery replete with Confederate graves.

Charter school teacher Bethany Lanier, 32, was walking in a mostly empty square in the Atlanta suburb of Decatur with Lindsay Futterman, 30, as they debated whether to get a drink at a pub.

If classes are canceled Friday, the charter school students will have missed nine days of school. To make up days, administrators have canceled a three-day break.

“Now, we’re out because we have cabin fever,” Lanier said as Futterman added: “It’s kind of annoying now.”

Many Southerners took to makeshift sleds on the ice and snow, with at least seven people hospitalized in sledding accidents just in Georgia. Four people were hurt sledding in a kayak that crashed into a pole, said Fire Chief Ricky Pruit in Cleveland, Ga. One victim suffered leg injuries, another was knocked unconscious and lost several teeth, and the other two refused treatment, he said.

Ice combined with wind gusts up to 30 mph snapped tree limbs and power lines. About 350,000 homes and businesses lost electricity in Georgia, South Carolina had about 245,000 outages, and North Carolina around 100,000. Some people could be in the dark for days.

As he did for parts of Georgia, President Barack Obama declared a disaster in South Carolina, opening the way for federal aid. There, a winter storm warning remained in effect, but the wintry mix was forecast to wrap up Thursday morning.

For the Mid-Atlantic and the Northeast, the heavy weather was the latest in an unending drumbeat of storms that have depleted cities’ salt supplies and caused school systems to run out of snow days.

Washington, D.C., could see around 8 inches of snow. Federal offices and both airports there were closed. Boston also could see 8 inches; New York City could receive 6. The Philadelphia area could get a foot or more, and Portland, Maine, may see 8 or 9 inches.

In Atlanta, which was caught badly unprepared by the last storm, area schools announced even before the first drop of sleet fell that they would be closed on Tuesday and Wednesday. Schools were also closed for Thursday. Many businesses in the corporate capital of the South shut down, too.

The scene was markedly different from the one Jan. 28, when thousands of children were stranded all night in schools by less than 3 inches of snow and countless drivers abandoned their cars after getting stuck in bumper-to-bumper traffic for hours and hours.

“I think some folks would even say they were a little trigger-happy to go ahead and cancel schools (Tuesday), as well as do all the preparation they did,” said Matt Altmix, who was out walking his dog in Atlanta on Wednesday. “But it’s justified.”