US weather: Winter storm sweeps across Canada and the US
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People in Montreal, Canada which has been hit by the storm
An arctic blast is expected to bring the coldest Christmas on record to North America.
The powerful winter storm is making its way through the US and Canada putting around 240 million people in the US alone under weather alerts.
It is so large that it stretches from coast to coast and as far south as the US-Mexico border and Florida.
The National Weather Service (NWS) for the USA said temperatures of -45C are possible by the end of this week in some parts of the country.
There are also warnings that high winds could bring hurricanes to parts of North America.
Meteorologists warn the storm could become a "bomb cyclone".
When the central pressure of a jet stream high in the atmosphere falls rapidly, it causes an explosive storm with intensifies rapidly, this is called a "bomb cyclone".
On Wednesday Calgary in Canada hit temperatures of -26C, its coldest December day for 26 years.
In Colorado, temperatures dipped to a record-breaking low of -9F from 42F on Thursday.
New York, Kentucky, North Carolina, West Virginia, Georgia and Oklahoma have all declared states of emergency.
In Chicago a winter storm warning is in place until Saturday
People are being warned not to travel and more than two thousand flights have been cancelled.
In Chicago, a winter storm warning is in effect until Saturday, winds are expected to go over 50mph (80km/h).
The National Weather Service has warned that even in built-up areas like the city of De Moines in Iowa, frostbite is a danger.
Frostbite is caused by extreme cold reducing blood flow to parts of the body, usually fingers and toes this damages the skin and tissue.
Nearly 177 million people in the US are under wind chill alerts. Parts of South Dakota, Wyoming and Montana have had wind chills below minus 45 degrees Celsius in the past two days.
"This is not like a snow day, when you were a kid, this is serious stuff," President Joe Biden said in a White House briefing on Thursday.