Almost 800,000 households are without power in the United States as a huge winter storm stretches from the southern Rocky Mountains in the west of the country to New England on the northeast coast.
Heavy snow, sleet and freezing rain are threatening almost 180 million people - more than half the population - the National Weather Service said. A total of 37 states are affected.
"The snow and ice will be very, very slow to melt and won't be going away anytime soon," said meteorologist Allison Santorelli.
Josh Weiss, a meteorologist at the National Oceanic and Atmospheric Administration, said there are two aspects that make this storm "unique": its broad spread, covering 2,000 miles of the country, and the extreme cold it is forecast to leave behind.
More than 10,000 flights have been cancelled on Sunday and another 8,000 delayed, according to flight tracking website FlightAware.
Sunday's cancellations are already the most on any single day since the COVID pandemic, said aviation analytics firm Cirium.
At least 17 states and the District of Columbia have declared emergencies, said homeland security secretary Kristi Noem.
"Stay home if possible," she advised.
Mikie Sherrill, the governor of New Jersey, said she was expecting conditions the "likes of which we haven't seen in years".
Announcing a 35mph speed limit on highways, she added: "It's a good weekend to stay indoors."
Almost 800,000 power outages were reported in the path of the winter storm, according to PowerOutage.us.
Tennessee was hardest hit with more than a quarter of a million customers losing their connections, while Texas, Louisiana and Mississippi all had more than 100,000 affected households.
In Louisiana, there were reports of vehicles hitting fallen trees and branches falling onto houses in the parish of DeSoto.
In Georgia, senior state meteorologist Will Lanxton said it was "perhaps the biggest ice storm we have expected in more than a decade".
Read more from Sky News:
'Sickening lies': Family of man shot dead by ICE speak out
Trump praises 'very brave' UK soldiers
In New York City, thousands of bin lorries had been fitted with snow ploughs, mayor Zohran Mamdani said.
This weekend, "each 12-hour shift will be staffed by more than 2,000 sanitation workers", he said in a video posted on X.
Temperatures will be at their coldest for eight years, he added.
(c) Sky News 2026: US weather: 800,000 without power as winter storm stretches from Colorado to New England
'Get the truth out about our son,' say family of man shot dead by federal officer in Minneapolis
'The normal rules of engagement have been thrown out - Alex Pretti was on his knees when first shot was fired'
'My son was wrongly identified by police after fatal crash - when mistake was uncovered, it was too late'
UK weather: Yellow warnings issued for heavy rain prompting fears of flooding
86 arrests after protesters breach Wormwood Scrubs prison grounds holding Palestine Action-linked activist
Time will tell if policing shake-up will leave people feeling better protected
Dozens still missing after landslide on Indonesia's Java island kills at least 11 people
'Strong case' for social media ban on children, says home secretary - but police won't be involved
National Police Service: New 'British FBI' to fight serious crime and help local police tackle everyday offences