More than 370,000 homes and businesses were still without power today in parts of central and northeastern US after a weekend ice and snow storm rolled across the region.
More than 7000 flights were behind schedule by late Monday night, many of those in New York, Washington and Chicago as people struggled to travel before Christmas.
At least 11 people in the US have been killed in the storm.
In Canada, police said two people in Ontario are dead from carbon monoxide poisoning after using a gas generator to heat their blacked-out home northeast of Toronto.
In Toronto alone Monday night, 11 people were taken to hospitals with signs of carbon monoxide poisoning.
The region was under a cold alert, with temperatures expected to be well below freezing Tuesday.
Toronto Mayor Rob Ford said 115,000 customers were still awaiting power, and officials said some may not have it restored until after Christmas.
Some US states kept emergency shelters open for people who would be without power.
About 250,000 of the people without power were in Michigan, whose largest utilities said it'll be days before power is restored because of the difficulty of working around broken lines.
In Maine, the number of customers without power spiked to more than 100,000.
Untreated roads and sidewalks will remain a slippery, dangerous mess.
Meanwhile, a severe winter storm caused major travel problems in parts of western Europe, stranding passengers travelling for Christmas at Paris and London airports and leaving tens of thousands of homes without power.
The storm caused four deaths in Britain, including a man who jumped into a fast-flowing river to try and rescue his dog. The severe weather also left a 12-year-old boy crushed to death beneath construction materials in Normandy, France.
In Britain, thousands of people trying to get away for the holidays were affected by reduced or cancelled train services due to landslides and fallen trees and flooded roads, Flight delays were triggered by power outages at London Gatwick Airport's North Terminal.
The airport, the country's second-largest, said it was investigating the cause of the outage, but said it was weather related.
Across the English Channel, nearly all long-haul flights out of Paris' Charles de Gaulle Airport were delayed because of the storm, according to the Paris airport authority website.
Electricity provider ERDF said the winds left nearly 200,000 homes in western France without electricity.
France's Interior Ministry says the 12-year-old boy was killed at a construction site in Saint Germain de Tallevande and another person was seriously injured.
The Energy Networks Association, which represents power companies across the UK, said 150,000 homes were without power, mainly in the south of England.
Power supplier Southern Electric said some may not get electricity back in time for Christmas Day.
The Environment Agency issued hundreds of flood warnings across all of England and Wales, with a severe flood warning - the highest level, warning of danger to life - in southwest England.
Two people died in car accidents, and one woman's body was pulled from a river in north Wales.
In Spain, extremely strong winds battered the northwestern Galicia region, and a tree that fell down on rail tracks prompted the derailment of a commuter train. None of the 10 passengers or the crew members were injured.
Wind speeds hit 185 kilometres per hour (115 mph) in some coastal areas of Galicia, and the region's fishing fleet stayed in port. As many as 88,000 homes lost electrical power, and crews were trying to restore it.