Tens of millions of people across the United States are bracing for a blast of cold weather that forecasters have warned could be life-threatening.
With temperatures set to drop to once-in-a-generation lows here is a selection of some of the best photographs.
A state of emergency has been declared in the Midwestern states of Wisconsin, Michigan and Illinois.
Other states not quite used to cold temperatures, including Mississippi and Alabama, are also preparing for cold conditions and snowfall.
Forecasters predict that Chicago, one of the country’s busiest cities, could get colder than Antarctica in the coming days.
Thousands of flights were cancelled on Tuesday and further travel disruption in coming days is expected.
Officials in a number of states have opened shelters as police search for people most at risk from cold conditions.
Frostbite could be possible within 10 minutes of exposure to the extreme weather, the National Weather Service has warned.
Schools in several states have announced blanket closures already.
“If you don’t have to be outside, don’t,” meteorologist Amy Seeley warned Chicago residents.
The weather system has also blanketed parts of Canada – prompting warnings of “hazardous” driving conditions and risks to health.
Record-breaking snowfall levels of 93cm (36in) were recorded at Ottawa airport on Tuesday.