In Pictures: US and Canada blanketed by frigid air

More than 142 million people across the US are under a wind chill alert on Monday, as frigid Arctic air hangs over much of the country.

The National Weather Service (NWS) said the heartland of the US will likely experience record-breaking cold.

Temperatures in Montana are forecast to plunge below -50F (-45C).

The deep freeze may affect voter turnout in Iowa, as the state gears up to choose its Republican candidate for the 2024 election.

In its advisory on Monday, the NWS warned of "brutally cold temperatures" that will persist until Wednesday.

The cold is thanks to an Arctic air mass that has travelled southeast into the US from western Canada - where it set record-low temperatures.

In Edmonton, Alberta, temperatures reached a bone-chilling record-low of -49.5F (-45.3C) on Saturday. The cold has strained Alberta's energy grid, and at one point the province issued an emergency alert asking people to turn off unnecessary appliances at the risk of widespread power outages.

As of Monday, all of Alberta remains under an extreme cold warning, with Environment Canada warning people to bundle up, as "frostbite can develop within minutes on exposed skin, especially with wind chill".

At least six million Canadians are under an extreme cold warning, mainly in Alberta, Saskatchewan and parts of British Columbia.

With much of that Arctic air mass now also hanging over the American heartland, political analysts are weighing whether the cold will hamper voter turn out in Iowa, where the state's caucuses are being held on Monday.

Iowa has been grappling with extreme cold and heavy snow for much of the weekend, forcing the cancellation of some campaign events,

On Monday, temperatures in some parts of the state are expected to dip as low as -40F (-40C) with the wind chill.

The winter weather has even disrupted the play-off the National Football League's play-off schedule.

A snowstorm in New York forced the Sunday wild-card round game between the Buffalo Bills and Pittsburgh Steelers to be rescheduled to Monday instead.

The AFC Wild Card game between the Kansas City Chiefs and the Miami Dolphins, however, went ahead as scheduled on Saturday, despite temperatures on the field reaching -28F (-33C) with the wind chill.

Elsewhere in the country, a mix of snow, sleet and freezing rain is expected across the Lower Mississippi Valley and the Tennessee Valley, supported in part by the frigid cold temperatures.

Out west, a winter storm watch has been issued for parts of Washington State, as well as Portland, Oregon, where ongoing power outages have forced more than 100,000 households and businesses to weather the cold without any heat or electricity for the last three days.

Cold temperatures in Texas have also knocked power out for nearly 25,000 others.

While the NWS anticipates there will be some relief from the cold by Wednesday, it will be short-lived.

Another surge of Arctic air is expected to travel southward from Canada later this week, which could lead to more frigid temperatures across the Midwest and deep South by Friday.