PHILADELPHIA — Yet another storm paralyzed the Northeast with heavy snow and sleet Thursday, giving the winter-weary that oh-no-not-again feeling, while hundreds of thousands across the ice-encrusted South waited in the cold for the electricity to come back on.
At least 21 deaths were blamed on the treacherous weather, including that of a pregnant woman struck by a mini-snowplow in a New York City parking lot as she loaded groceries into her car.
The sloppy mix of snow and face-stinging sleet grounded more than 6,500 flights and closed schools and businesses as it made its way up the heavily populated Interstate 95 corridor, where shoveling out has become a weekly — sometimes twice-weekly — chore.
‘‘Snow has become a four-letter word,’’ lamented Tom McGarrigle, a politician in suburban Philadelphia.
About 1.2 million homes and businesses lost power as the storm moved from the South through the Northeast. By Thursday evening, about 550,000 customers remained in the dark, mostly in South Carolina and Georgia.
Baltimore awoke to 15 inches of snow. Washington, D.C., had at least 8, and federal offices and the city’s two main airports were closed. The Virginia-West Virginia state line got more than a foot.
Philadelphia had nearly 9 inches, its fourth 6-inch snowstorm of the season — the first time that has happened in the city since record-keeping began in the late 1800s. New York City received nearly 10 inches, and parts of New Jersey had more than 11.
The Boston area was expecting 4 to 6, while inland Connecticut and Massachusetts were looking at a foot or more.
In some places, the snow and freezing rain eased up during the day, but a second wave was expected overnight into Friday.
‘‘It’s like a dog chasing its tail all day,’’ said Pat O'Pake, a plow operator in Pennsylvania.
In New Cumberland, Pa., which had about 10 inches of snow by midafternoon, Randal DeIvernois had to shovel after his snow blower conked out.
‘‘Every time it snows, it’s like, oh, not again,’’ he said. ‘‘I didn’t get this much snow when I lived in Colorado. It’s warmer at the Olympics than it is here. That’s ridiculous.’’
In New York, Min Lin died after she was struck by a utility vehicle with a snowplow attached to it as it backed up outside a shopping center in Brooklyn. Her nearly full-term baby was delivered in critical condition via cesarean section.
No charges were brought against the snowplow operator in what appears to have been an accident, police said.
Across the South, the storm left in its wake a world of ice-encrusted trees and driveways and snapped branches and power lines.
In Bonneau, S.C., Jimmy Ward and his wife, Cherie Ward, lost power and spent Wednesday night in their home, warming themselves in front of a gas log fire.
But after running low on propane, they headed Thursday night for a hotel, where it was expected to be cozier but a lot less exciting than the night before.
‘‘From 2 o'clock yesterday until this morning, it just sounded like gunfire — all the trees popping and falling,’’ Cherie Ward said.
In North Carolina, where the storm caused huge traffic jams in the Raleigh area on Wednesday as people left work and rushed to get home in the middle of the day, National Guardsmen in high-riding Humvees patrolled the snowy roads, looking for any stranded motorists.
Some roads around Raleigh remained clogged with abandoned vehicles Thursday morning. City crews worked to tow them to safe areas where their owners could recover them.
The storm didn’t leave animals alone, either. In Maryland, Prince George’s County fire officials said a horse that had slipped inside a snowy barn and gotten stuck on its side was euthanized after failing to show signs of improvement.
Around the country, this is shaping up as one of the snowiest winters on record. As of early this month, Washington, Detroit, Boston, Chicago, New York and St. Louis had gotten roughly two or three times as much snow as they normally receive at this point in the season.
The procession of storms and cold blasts — blamed in part on a kink in the jet stream, the high-altitude air currents that dictate weather — has cut into retail sales across the U.S., the Department of Commerce said. Sales dipped 0.4 percent in January.
This latest round of bad weather threatens to disrupt deliveries of flowers for Valentine’s Day on Friday.
‘‘It’s a godawful thing,’’ said Mike Flood, owner of Falls Church Florist in Virginia. ‘‘We’re going to lose money. There’s no doubt about it.’’
Ronald Reagan Washington National Airport was virtually silent, with all flights canceled. Travelers tried to catch some sleep in the terminals.
Rob Wolcott, of Washington, and his wife were trying to reach the Caribbean island of St. Kitts, where he was planning to officiate at a friend’s wedding on Saturday.
The future bride and groom are ‘‘a little stressed,’’ Wolcott said. ‘‘But they'll figure something out. They will still get married, whether or not I am the one to do the actual officiating.’’
On the National Mall in Washington, 8-year-old Lucas Moore was having fun with his father and thinking about how all the snow days he has had this year may come back to haunt him.
‘‘If they do cut into summer, I'm going to be, like, really mad and trying not to go to school,’’ he said. ‘‘When it’s summer, play time.’’
In New York City, the teachers union and TV weatherman Al Roker harshly criticized Mayor Bill de Blasio’s decision to keep schools open. Roker, who was in Russia for the Winter Olympics but has a daughter in New York’s public schools, said on Twitter: ‘‘It’s going to take some kid or kids getting hurt before this goofball policy gets changed.’’
The mayor said many parents depend on schools to watch over their children while they are at work.Associated Press writers Kevin Begos in Pittsburgh; Michael Rubinkam in Berks County, Pa.; Kathy Matheson in Philadelphia; Sarah Brumfield and Brett Zongker in Washington; Matthew Barakat in Falls Church, Va.; and David Dishneau in Frederick, Md.; contributed to this report.