As a powerful winter storm continues to batter North America, more than one million people in the United States and Canada will be without power on Christmas Day.
When air pressure falls, a bomb cyclone occurs, bringing snow, severe winds, and subfreezing temperatures.
The storm, extending more than 2,000 miles (3,200 km) from Quebec to Texas, impacted nearly 250 million people.
And the authorities have linked at least 19 fatalities to the weather event.
Several storm-related fatalities have involved road traffic accidents.
They include a 50-car pile-up in Ohio that killed four motorists. Another four died in separate crashes in the state.
Airlines have cancelled thousands of flights over the holiday season, while freeze advisories are in effect even in Florida and Georgia, two typically milder southern states.
Only California, where continental mountain ranges are helping to insulate the Golden State, has mainly avoided the chilly weather.