Nearly 100 million people in Canada and the US are braced for some of the coldest air on earth, as a record deep-freeze hits North America.

The frigid blast could bring "once-in-a-generation" wind chills that cause frostbite in less than 10 minutes, the National Weather Service has warned.

Residents from Manitoba to Maine are being urged to limit their time outdoors until Saturday.

At least 11 people have died in the bad weather in the US south since Monday.

There were eight fatalities in Texas, two in Oklahoma and one in Arkansas.

The expected drop in temperatures is attributed to a powerful Arctic front that stretches from the Canadian maritime provinces to the core of the US.

About a dozen records were expected to be broken by Friday in several US states, where a total of 82 million people were forecast temperatures of -17 Celsius (0 F) or lower.

In Maine, for example, parts of the state were expecting the lowest temperatures recorded since 1971. In the city of Portland, wind chill was expected to reach -41 F (-40.5 C).

In nearby Burlington, Vermont, Friday's highest temperature was expected to reach just -20 C (-5 F).

Boston is currently under a cold emergency. Public schools have been closed in the city, as well as in nearby Worcester and in Buffalo, New York.

New York City - which could see wind chills as low as -10F (-23C) - has enacted a "code blue", an emergency designation that allows the homeless to go to any shelter to seek warmth.

Other major cities are also expected to bottom out in the single digits Fahrenheit (around -13 C to -17 C) by Saturday, although forecasters predict they will rebound by the end of the weekend.

The Midwestern states of Michigan, Wisconsin, Indiana, Illinois and Ohio were also not spared by the freezing temperatures.

Parts of Canada are expecting temperatures anywhere between -38C to -50C (-36.4F to -58F). An extreme cold advisory issued by Environment Canada on Friday morning has blanketed the Maritimes, most of Quebec and all of Ontario, spilling into Manitoba.

In Ottawa, Canada's capital city, the extreme cold forced the closure of a local ski hills and outdoor ice-skating trails. In Toronto, the wind chill plunged the temperature to -29C (-20F) on Friday.

The brutal winter weather follows this week's deadly ice storm in parts of Texas, where temperatures have begun to climb above freezing, and ice was expected to melt on Friday.

More than 250,000 people were without power as of Friday evening in Texas, Arkansas, Mississippi, Tennessee and New York, according to poweroutage.us.–BBC