A man braves the brisk weather as a cold snap grips Ottawa in Canada.

Ottawa - Arctic air sweeping through Canada and parts of the United States sent temperatures plunging to record lows on Wednesday with a wind chill of minus 40 degrees Celsius.

Canada was the coldest nation in the world at the start of the day with with temperatures as low as minus 43.1 degrees Celsius in the Northwest Territories, according to public broadcaster CBC.

In Ottawa, buildings cracked in the cold, making sounds like the crash of a wrecking ball.

No significant damage was reported, and only one death has been linked to the cold - a man found dead in Toronto with signs of hypothermia.

In Rouyn, Quebec, temperatures dropped to minus 40.3 Celsius - lower even than in Yakutsk, Siberia, which came in at minus 38.8 Celsius.

“Low pressure in southern Canada brought a cold air mass from the north,” causing a deep freeze, Environment Canada meteorologist Andre Cantin told reporters.

The cold snap was being felt as far south as the US states of Virginia and Ohio, where severe cold warnings pointed to risks of hypothermia and frostbite, as well as carbon monoxide poisoning from poorly ventilated heating sources.

The cold air is expected to linger until at least the end of the week, weather forecasters said.

In the Canadian capital, dogs resisted going out for their morning walk, and many bureaucrats stayed home.

American singer Miley Cyrus and her fiance Liam Hemsworth, underdressed in sweatshirts for a trek to a downtown bookstore, reportedly said they were “freezing” after just coming from Costa Rica.

Hemsworth, who starred in The Hunger Games, was in town working on a film.

Schools were closed across eastern Canada, and 5 000 homes were without electricity in Quebec province.

In Montreal and Toronto, shelters offering a bed and a hot meal quickly filled up overnight.

New York City opened scores of warming centres, where anyone can go and thaw out during daytime hours. In neighbouring Connecticut, Governor Dannel Malloy urged similar measures.

“Overnight temperatures over the next few days are expected to range from zero to 10 degrees. Factor in the wind chill, and it will feel like zero to minus 15 degrees,” he wrote on his Facebook page.

“We are also encouraging local communities to consider opening warming centres or other facilities to help people in need,” he said.

The cold was most painful in areas of New York where electric power and other infrastructure remains battered in the wake of Superstorm Sandy.

“It's cold, like we're outside, because once the generator's cut, that's it: no power, no lights, anything. No heat,” Sandra Green, a resident in the badly hit coastal Rockaways neighbourhood, told WCBS 880 radio.

“What I will do if it goes that way without the heat, I'll set the house on fire and I will stand beside it and stay warm,” another resident of the devastated area told the radio.

Washington was still far from its all-time record low of minus 26 degrees Celsius set on February 11, 1899, the day of a severe cold wave from Maine to Florida that preceded the Great Blizzard of 1899.

But it was enough to send a shiver through the US capital two days after the public inauguration of President Barack Obama's second term - an event that saw an estimated one million people brave the winter chill.

By late morning the temperature in Washington was minus six Celsius, but a 15km/h wind from the north-west made it feel more like minus 11 under partly sunny skies. - Sapa-AFP