North America arctic blast arrives in the east
Commuters in Washington DC bundled up against wind chill temperatures as low as -6F (-21C) A brutal blast of arctic air has settled over eastern North America, bringing dangerously low temperatures not seen in decades.
About half of the US population has been placed under a wind chill warning or cold weather advisory.
In Toronto, the temperature dropped to -24C (-11F) before dawn on Tuesday.
Air, rail and road travel remain snarled by high, freezing wind, and residents have been warned to stay indoors to avoid frostbite.
Cold air broke records in Chicago on Monday, where the temperature of -16F (-27C) was the lowest ever seen on that date.
It was one of more than 120 daily temperature records broken in cities across the US since the beginning of 2014, many dating back decades.
Sharp temperature dropThe arrival late on Monday of the arctic weather pattern caused temperatures to plummet overnight in New York and Washington DC by as much as 45 degrees in a matter of hours, from unseasonably warm highs a day earlier.
New York Governor Andrew Cuomo closed parts of major highways across his state in preparation for the extreme weather.
Adding to the misery, forecasters say the areas on the eastern shores of the Great Lakes could again be blanketed by snow, as the cold air moved over the water.
In Canada, 4,000 residents of Quebec and 1,000 in Newfoundland were still without power on Tuesday amid the freezing temperatures and snow.
The polar blast was threatening crops and livestock across the American farm belt, even in the usually temperate Deep South. The freeze was expected to reach as far south as Texas and central Florida, the National Weather Service said.
Meteorologists said some 187 million people in all would feel the effects of the cold by Tuesday.
South Pole coldThe cold temperatures have been widely blamed on a shift in the weather pattern known as the "polar vortex", creating some extreme temperatures.
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The freezing, gusty winds have already forced the cancellation of 2,300 flights on Tuesday and have also caused widespread road and rail delays.
JetBlue Airways suspended nearly all operations at airports in Boston and around New York City on Monday, but hoped to be "100% operational" by 15:00 eastern US time (20:00 GMT) on Tuesday.
Toronto's Pearson Airport was at a full ground stop until 09:00 local time (14:00 GMT) with passengers waiting in lines and in planes on tarmacs for several hours, the CBC reported.
More than 500 passengers on their way to Chicago were stuck overnight in northern Illinois on three Amtrak passenger trains after drifting snow and ice covered the tracks.
Train officials said it was safer to keep passengers on board with heat and food than attempt to transfer them to buses in the freezing temperatures and deep snow.
The stuck trains were unloaded on Tuesday morning, with passengers expected to take buses back to Chicago.
In Illinois, the National Guard used 10-tonne military vehicles to clear up after several lorries slid off the road, stranding nearly 400 vehicles. There were no fatalities or injuries reported in those incidents.
Indiana state government employees were told to stay home and in the state capitol of Indianapolis, it has temporarily been made illegal to drive except in an emergency or to seek shelter, in order to keep the roads free for emergency vehicles.
The weather has been blamed for at least 16 deaths in recent days, including:
- A one-year-old boy in Missouri who was killed in a car collision with a snowplough
- A worker at a Philadelphia salt storage facility who died when a 100-ft (30-m) pile of road salt collapsed on him
- An Oklahoma man who was killed when his vehicle skidded off an icy road
- An elderly woman suffering from Alzheimer's disease who froze to death after getting lost in New York state
- Four men across Illinois who suffered fatal heart attacks while shovelling snow
BBC Weather's Alex Deakin delves into the polar vortex
The state of Minnesota and the city of Chicago, Illinois, have ordered all schools closed.
It was so cold that even the polar bear at Chicago's Lincoln Park Zoo was kept indoors, CNN reports.
Some relief was in sight in the Midwest, as the cold air pattern moved eastward, the National Weather Service said.
Ice builds up along Lake Michigan in Chicago, Illinois 
As far south as Oklahoma, a horse drinks water from a hole in a frozen water tank 
A woman attempts to plough her driveway in New York 
A shopper fights the elements in a grocery store car park in Michigan 
A lorry stranded in a ditch in Illinois 
A worker in Muskegon, Michigan, clears snow from the front of local businesses 
Homeless men use donated firewood to beat cold temperatures in Knoxville, Tennessee Send your pictures and videos to yourpics@bbc.co.uk or text them to 61124 (UK) or +44 7624 800 100 (International). If you have a large file you can upload here.
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