More than one million Americans and Canadians are facing Christmas Day without power as a major winter storm sweeps across North America.
A bomb cyclone, when atmospheric pressure drops, brings snow, strong winds and freezing temperatures.
About 250 million have been affected, and at least 19 have died from the storm, which stretched more than 2,000 miles (3,200 km) from Quebec to Texas.
Thousands of flights have been canceled during the festival.
The western US state of Montana has been hardest hit by the cold, with temperatures dropping to minus 50F (-45C).
Near whiteout conditions have been reported in Minnesota, Iowa, Wisconsin and Michigan. In Buffalo, New York, the US National Weather Service (NWS) reported “zero mile” visibility.
In the Pacific Northwest, some residents ice-skated the frozen streets of Seattle and Portland.
The northeastern New England region of the US has seen coastal flooding, inundating communities and downing power lines.
Even the normally mild southern states of Florida and Georgia face severe freeze warnings.
The only region that has largely escaped cold weather is California, where continental mountain ranges are helping to protect the Golden State.
In Canada, the provinces of Ontario and Quebec were under the brunt of the Arctic blast.
Much of the country, from British Columbia to Newfoundland, was under severe cold and winter storm warnings.
Many of the deaths from the storm involved road traffic accidents, including a 50-car pileup in Ohio that killed four motorists. Four more died in separate accidents in the state.
A shortage of snowplow operators was causing travel problems across the country, which was being blamed on low pay rates.
The NWS says more than 100 daily cold temperature records could be set or broken over the next few days.
