A brutal winter storm smacked United States' south-east with a rare blast of snow and ice on Wednesday, hitting parts of Florida, Georgia and South Carolina with their heaviest snowfall in about 30 years.
Forecasters warned that the same system could soon strengthen into a "bomb cyclone" as it rolls up the East Coast, bringing hurricane-force winds, coastal flooding and more snow.
At least 17 deaths were blamed on dangerously cold temperatures that for days have gripped wide swaths of the US from Texas to New England.
A winter storm warning extended from the Gulf of Mexico of Florida's "Big Bend" region and all along up the Atlantic coast. Forecasters said hurricane-force winds blowing offshore on Thursday could generate seven-metre waves in the sea.
Schools were closed in the south-east months after being shut down because of hurricane threats. Police urged drivers to stay off the roads in a region little accustomed to the kind of winter woes common to the north-east.
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America's big freeze - in pictures
Record-shattering US cold reaches into Florida
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In Savannah, snow blanketed the city's lush downtown squares and collected on branches of burly oaks for the first time in nearly eight years. William Shaw used baby steps to shuffle along a frozen road from his home to the post office.
"It almost seems the town is deserted just like in the last hurricane," said Mr Shaw, 65. "There's no one on the street. It's got a little eerie feeling."
Lorries spread sand on major streets in Savannah ahead of the storm and police closed several bridges, overpasses and a major causeway because of ice.
By the time the morning's dreary sleet and rain turned to fluffy snow, Savannah came out to play. Families with children flocked to Forsyth Park near the downtown historic district for snowball fights. The National Weather Service recorded 3cm of snow — Savannah's first measurable snowfall since February 2010 and the deepest in 28 years.
In Pensacola, Florida, Alex Vieira was surprised to find his swimming pool had frozen over.
Frozen swimming pool
The rare sub-zero temperatures caused it to freeze solid, much to the delight of his sons, who promptly bounced a football off the solid surface, Mr Vieira said.
Across the Georgia-South Carolina line in Charleston, the weather service reported 12.7cm as the snow was winding down at 5pm - their heaviest snowfall since December 1989 - and plenty for Chris Monoc's sons, ages four and two, to go sledding outside their home near the city's iconic Ravenel Bridge.
"They probably will be teenagers the next time something like this happens, and that's kind of sad," he said. "We'll enjoy it while it is here."
The areas airports were closed and airlines cancelled 500 flights on Wednesday. A further 1,700 more were cancelled on Thursday. Interstate 95 was nearly an icy parking lot for almost all of its 200 miles (322 kilometers) in South Carolina. State Troopers could not keep up with the number of reported wrecks which numbered in the hundreds.
The weather service said the winter storm will probably intensify into a "bomb cyclone" that could dump more than 20cm of snow in Boston on Thursday and 15cm of snow in the New York City region.
US braces for 'Winter Bomb'
Meteorologists have been using the term "bomb" for storms for decades, but the phrase went viral on social media on Wednesday. A storm is a bomb — or bombogensis happens — when it drops 24 millibars of pressure in 24 hours. This storm looks like it will intensify twice that rate, said Bob Oravec, lead forecaster at the National Weather Service's Weather Prediction Center.
Mississippi's largest city said record cold is breaking water mains, leaving some customers with little or no water flow.
Jackson city spokeswoman Kai Williams said Wednesday evening that the city knew of 37 separate water main breaks that it attributed to cold. The city has declared an emergency and is hiring outside contractors to help repair water main breaks.
Blizzard warnings were issued from Rhode Island to Maine. Mr Oravec said he expects they could be extended as far south as parts of New York.
"It's sort of akin to a hurricane traveling up the coast," says Ryan Maue, a meteorologist at the private firm Weather.us.
Boiling water
Georgia Govenor Nathan Deal declared a state of emergency through Friday for 28 counties. School systems on the Alabama coast ditched school uniforms so students could bundle up in warmer clothing.
Florida's largest theme parks announced that water attractions such as Disney's Typhoon Lagoon, Universal Orlando's Volcano Bay and SeaWorld's Aquatica were closed. Temperatures were running well below normal for this time of year, and the lows are expected to hover right around freezing.
In Prairieville, Louisiana, Valerie Anne Broussard struggled overnight to keep warm in a house that is being rebuilt after the 2016 floods that hit the small community southeast of Baton Rouge. Her home has exterior walls and floors but no insulation, no central heating and only a few working electrical outlets. Eggs that she left on the kitchen counter froze and broke open.
"It's like a camping trip that I didn't sign up for," said Ms Broussard, who's been huddling with her 8-year-old daughter, newborn and boyfriend in a bedroom warmed by space heaters.
Making the most of the South's bitter cold snap, the North Carolina Zoo in Asheboro offered discounted tickets for those willing to brave the cold to see polar bears frolic in their kind of weather, along with Arctic foxes and elk. African elephants, lions and gorillas were sheltered out of public view.
As the cold pushed farther northward, Jerry Gorans found himself stunned by the frigid temperatures as he walked along the waterfront City Dock of Annapolis, Maryland, where birds stood still on icy water.
"This is the coldest I've been in probably 50 years," said Mr Gorans, who lives in Fresno, California, and was visiting his wife's family in Maryland.
"I mean, this is freezing cold. My feet hurt, my ears hurt."
