Parts of America are enduring temperatures colder than Antarctica this week as a blast of Arctic air from the polar vortex has caused the mercury to plunge as low as -40C (-40F).

US officials are urging residents from northern states to stay inside as the deep freeze sets in across the country, bringing with it life-threatening conditions that have forced rail workers in Chicago to start track fires to keep them warm enough to function, and led to warnings not to breathe too deeply when outside.

Brian Hurley, a meteorologist with the National Weather Service's weather prediction centre in Maryland, said: “The heart of this cold ... is hitting us now. A lot of records are going to fall.”

In at least 10 states, the US Postal Service has said delivery service faces disruption - a rare occurrence for a government agency that boasts of never letting weather get in the way of a mailperson and their route.

"Due to the extreme weather conditions caused by Winter Storm Jaden, we have temporarily suspended delivery service in certain locations to ensure the safety and well-being of our employees," the agency tweeted. "Visit our Service Alerts page for more details."

Polar vortex brings temperatures colder than Antarctica to the US Show all 52 1 /52 Polar vortex brings temperatures colder than Antarctica to the US Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice covers the Lake Michigan shoreline Getty Polar vortex brings temperatures colder than Antarctica to the US Minnesota A firefighter walks past an ice-encrusted home after an early morning house fire AP Polar vortex brings temperatures colder than Antarctica to the US Ontario People walk in a park on the US side of Niagara Falls AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Massachusetts Mike Calen, left, and Steve Goyette, right, prepare to tie off as the ice covered fishing boat, Buzzards Bay, arrives at New Bedford harbour AP Polar vortex brings temperatures colder than Antarctica to the US Pedestrians protecting their faces from the cold in New York City, in Washington DC, along Lake Michigan's ice covered shoreline, in the Brooklyn borough of New York, in Chicago, in Kingston, Ontario, and in Montreal AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago Snow and ice covers Soldier Field Getty Images Polar vortex brings temperatures colder than Antarctica to the US Chicago Gas-burning heaters are placed on railroad tracks as Metra commuter train passes by EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice builds up along the shore of Lake Michigan Getty Images Polar vortex brings temperatures colder than Antarctica to the US Ontario A tree is covered in ice from the mist at park beside the falls in Niagara Falls AFP/Getty Images Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Water vapor rises above St. Anthony Falls on the Mississippi River beneath the Stone Arch Bridge AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Massachusetts Ice flows fill the Merrimack River as it heads towards the Atlantic Ocean in Newburyport AFP/Getty Images Polar vortex brings temperatures colder than Antarctica to the US Ontario A tourists take pictures of the Canadian Horseshoe falls in Niagara Falls AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Sub-zero temperatures produce icicles that hang from a restaurant EPA Polar vortex brings temperatures colder than Antarctica to the US Ontario A person takes a selfie beside on the US side of Niagara Falls AFP/Getty Images Polar vortex brings temperatures colder than Antarctica to the US The marsh around Logan Airport in Boston, Massachusetts remains frozen January 31, 2019 on a day where over 2000 flights were cancelled and delayed due to extreme cold and ice conditions caused by the Polar Vortex over the midwest and northern parts of North America. - A brutal cold wave moved eastward Thursday after bringing temperatures in the US Midwest lower than those in Antarctica, grounding flights, closing schools and businesses and raising fears of hypothermia. The extreme weather has now been blamed for as many as eight deaths, US news outlets reported. (Photo by Joseph PREZIOSO / AFP)JOSEPH PREZIOSO/AFP/Getty Images JOSEPH PREZIOSO AFP/Getty Images Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Water vapor from the Mississippi River envelopes a bridge as sub-zero temperatures produce dangerous windchills EPA Polar vortex brings temperatures colder than Antarctica to the US New York Pedestrians walk through the falling snow in the Financial District Getty Polar vortex brings temperatures colder than Antarctica to the US Ontario Steam rises from the US Niagara Falls before sunrise AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago Snow covers Wrigley Field entrance Reuters Polar vortex brings temperatures colder than Antarctica to the US New York Workers shovel at the entrance to City Hall in whiteout conditions Reuters Polar vortex brings temperatures colder than Antarctica to the US NASA's 'Blue Marble' data set of weather systems over the continental United States US National Oceanic and Atmospheric Administration/EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice and snow builds up along Lake Michigan EPA Polar vortex brings temperatures colder than Antarctica to the US Minneapolis epa07332136 Sub-zero temperatures that has also produced dangerous windchills made headlines in Minneapolis, Minnesota, USA, 30 January 2019. The US Midwest is gripped by a coldspell as a polar vortex sent temperatures far below zero degrees Celsius. EPA/CRAIG LASSIG CRAIG LASSIG EPA Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Chuck Carpenter is frost covered as he goes for a walk EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago A man walks along the lakefront as temperatures hovered around -20 degrees Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago Frozen Chicago River Reuters Polar vortex brings temperatures colder than Antarctica to the US New York A man walks next to a subway train as heavy snow falls AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago A digital board shows flight cancellations at Terminal 3 at O'Hare International Airport EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago A pedestrian stops to take a photo by Chicago River, as bitter cold phenomenon called the polar vortex has descended on much of the central and eastern United States, in Chicago, Illinois, U.S., January 29, 2019. REUTERS/Pinar Istek STRINGER Reuters Polar vortex brings temperatures colder than Antarctica to the US Chicago A shirt that was hung is seen frozen Terry Greenbeans/Reuters Polar vortex brings temperatures colder than Antarctica to the US Chicago People walk along the lakefront Getty Images Polar vortex brings temperatures colder than Antarctica to the US New York A young man waits on a subway platform in freezing temperatures AFP/Getty Images Polar vortex brings temperatures colder than Antarctica to the US Chicago Mist rises from the city and Lake Michigan EPA Polar vortex brings temperatures colder than Antarctica to the US New York People walk through the snow in lower Manhattan Getty Images Polar vortex brings temperatures colder than Antarctica to the US Chicago The James Versluis breaks ice on the frozen Chicago River near Navy Pier EPA Polar vortex brings temperatures colder than Antarctica to the US Michigan Aftermath of an accident in Grand Rapids, Michigan, U.S., January 29, 2019 in this picture obtained from social media. Picture taken January 29, 2019. JASON COFFELT/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES SOCIAL MEDIA Reuters Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Jen Brackman and Aaron Brackman don large jackets and goggles while on a walk on the Stone Arch Bridge on January 29, 2019 in Minneapolis, Minnesota. - The polar vortex is here -- tens of millions of people in the US braced on January 29, 2019, for a deep arctic chill, which authorities say could be life-threatening. Sub-zero temperatures already blanketing parts of Canada were already sweeping across the US Midwest and towards the East Coast. (Photo by STEPHEN MATUREN / AFP)STEPHEN MATUREN/AFP/Getty Images STEPHEN MATUREN AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago epa07331480 Steam rises from the city as the sun rises in Chicago, Illinois USA, 30 January 2019. The US Midwest is bracing for a cold spell as a polar vortex sent temperatures plummeting below zero degrees Celsius. EPA/KAMIL KRZACZYNSKI KAMIL KRZACZYNSKI EPA Polar vortex brings temperatures colder than Antarctica to the US New York Man moves luggage in snow during a winter storm in Buffalo, New York, U.S., January 30, 2019. REUTERS/Lindsay Dedario LINDSAY DEDARIO Reuters Polar vortex brings temperatures colder than Antarctica to the US Chicago epa07330187 Ice and snow builds up along Lake Michigan in Chicago, Illinois, USA, 29 January 2019. The US Midwest is braced with a coldspell as a polar vortex sent temperatures far below zero degrees Celsius. According to meteorologists temperatures in Chicago area can drop to minus 31 degress Celsius (-25F). EPA/KAMIL KRZACZYNSKI KAMIL KRZACZYNSKI EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice forms along the shore of Lake Michigan before sunrise, Wednesday, Jan. 30, 2019, in Chicago. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures on Wednesday, triggering widespread closures of schools and businesses, and prompting the U.S. Postal Service to take the rare step of suspending mail delivery to a wide swath of the region. (AP Photo/Kiichiro Sato) Kiichiro Sato AP Polar vortex brings temperatures colder than Antarctica to the US Michigan The city skyline is seen from the North Avenue Beach at Lake Michigan, as bitter cold phenomenon called the polar vortex has descended on much of the central and eastern United States, in Chicago, Illinois, U.S., January 29, 2019. REUTERS/Pinar Istek STRINGER Reuters Polar vortex brings temperatures colder than Antarctica to the US New York The sun rises behind icicles formed on the harbor in Port Washington, Wis., on Wednesday, Jan. 30, 2019. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures. (AP Photo/Jeffrey Phelps) Jeffrey Phelps AP Polar vortex brings temperatures colder than Antarctica to the US Chicago CHICAGO, ILLINOIS - JANUARY 30: A commuter walks through downtown in sub-zero temperatures during an extremely light morning rush hour on January 30, 2019 in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures. (Photo by Scott Olson/Getty Images) Scott Olson Getty Polar vortex brings temperatures colder than Antarctica to the US New York Geese huddle in the water as the sun rises at the harbor in Port Washington, Wis., on Wednesday, Jan. 30, 2019. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures. (AP Photo/Jeffrey Phelps) Jeffrey Phelps AP Polar vortex brings temperatures colder than Antarctica to the US Chicago epa07330193 Ice and snow builds up along Lake Michigan in Chicago, Illinois, USA, 29 January 2019. The US Midwest is braced with a coldspell as a polar vortex sent temperatures far below zero degrees Celsius. According to meteorologists temperatures in Chicago area can drop to minus 31 degress Celsius (-25F). EPA/KAMIL KRZACZYNSKI KAMIL KRZACZYNSKI EPA Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Icicles form outside a bridal shop on January 29, 2019 in Minneapolis, Minnesota. - The polar vortex is here -- tens of millions of people in the US braced on January 29, 2019, for a deep arctic chill, which authorities say could be life-threatening. Sub-zero temperatures already blanketing parts of Canada were already sweeping across the US Midwest and towards the East Coast. (Photo by STEPHEN MATUREN / AFP)STEPHEN MATUREN/AFP/Getty Images STEPHEN MATUREN AFP/Getty Polar vortex brings temperatures colder than Antarctica to the US Chicago A person walks along the lakeshore, Wednesday, Jan. 30, 2019, in Chicago. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures on Wednesday, triggering widespread closures of schools and businesses, and prompting the U.S. Postal Service to take the rare step of suspending mail delivery to a wide swath of the region. (AP Photo/Kiichiro Sato) Kiichiro Sato AP Polar vortex brings temperatures colder than Antarctica to the US Chicago Icicles form on the walkway at North Avenue Beach of Lake Michigan in Chicago, Illinois, U.S., January 29, 2019. REUTERS/Pinar Istek STRINGER Reuters Polar vortex brings temperatures colder than Antarctica to the US Chicago epa07330640 Men walk by a sign warning of falling ice in Chicago, Illinois, USA, 29 January 2019. The US Midwest is braced for a coldspell as a polar vortex send temperatures far below zero degrees Celsius. According to meteorologists temperatures in Chicago area could drop to minus 31 degress Celsius (-25F). EPA/KAMIL KRZACZYNSKI KAMIL KRZACZYNSKI EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago epa07331476 The sun rises over Lake Michigan in Chicago, Illinois, USA, 30 January 2019. The US Midwest is bracing for a cold spell as a polar vortex sent temperatures plummeting below zero degrees Celsius. EPA/KAMIL KRZACZYNSKI KAMIL KRZACZYNSKI EPA Polar vortex brings temperatures colder than Antarctica to the US Chicago CHICAGO, ILLINOIS - JANUARY 30: Commuters walk through downtown in sub-zero temperatures during an extremely light morning rush hour on January 30, 2019 in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures. (Photo by Scott Olson/Getty Images) Scott Olson Getty

North Dakota has seen temperatures drop as low as -32C (-25F), with wind chills at -52C (-62F) in Minnesota. The chill is expected to reach a wide swath of the US, with cities from Fargo, North Dakota to Minneapolis and Chicago, where temeratures have dipped below -26C (-15F). Accuweather says that there will also be temperatures drop below 0C (single digits in Fahrenheit) in cities and areas around Kansas City, Missouri, St Louis, Cincinnati and Pittsburgh.

All time record lows are expected in northern Indiana, with -46C (-50F) temperatures in that region.

In Des Moines, Iowa, the National Weather Service warned that "this is the coldest air many of us will have ever experienced", and suggested than anyone who goes outside should "avoid taking deep breaths, and minimise talking" while in the chill.

With the freezing temperatures bringing temperaturs unseen in a generation, residents have been told to be wary of hypothermia and frostbite from the arctic blast, which is expected to last for another eight weeks.

“I cannot stress how dangerously cold it will be,” AccuWeather meteorologist Rob Richards told USA Today. "An entire generation has gone by without experiencing this type of cold."

Shelters have been set up in some locations to protect the most vulnerable.

In Chicago, blustery weather could mean wind chills break the current record low of -33C (-27F) recorded in the city at O'Hare airport on January 1985.

Some places in the Midwest will likely be colder than the South Pole, which is around -25C (-13F) to -27C (-17F) this week.

Illinois governor JB Pritzker issued a statewide disaster proclamation, warning the weather “poses a serious threat” to residents.

“This storm poses a serious threat to the well-being of people around the state, and we will use every tool at our disposal to keep our residents safe,” he said in a statement. “This disaster proclamation ensures that the state of Illinois has the flexibility to effectively and efficiently respond to the needs of local governments during this extreme weather event.”

At least four deaths were linked to the dangerous weather system, including a man struck by a snow plough in Chicago, a young couple whose car struck another on a snowy road in northern Indiana, and a Milwaukee man found frozen to death in a garage.

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Chicago O'Hare and Chicago Midway international airports cancelled almost 2,000 flights in the early hours of Wednesday as the wintry weather gripped the Windy City.