The icy winds blasting the US have the power to freeze bare skin and kill animals.
Temperatures in the Midwest are plummeting as low as 30 degrees below freezing in a potentially deadly “polar vortex”.
People are being warned to stay inside to avoid dangerous wind chills of down to -50C.
Animals and livestock left unprotected in the gusts can be frozen to the ground they are sitting on.
According to the US National Weather Service, bare skin can be frozen in less than five minutes.
The risk of frostbite increases with lower air temperatures and colder winds.
North Dakota is battling temperatures of -35C, which will freeze skin in less than five minutes with winds above 20mph.
In a warning issued for today, the weather service said: “The combination of very cold air and strong winds will create dangerously low wind chill values.
“This will result in frostbite and lead to hypothermia or death if precautions are not taken.”
Fingers, toes, ear lobes and the nose are most susceptible to frostbite, which can need amputation if not treated in time.
The biting wind chill can also bring on hypothermia rapidly, where the body temperature falls abnormally low.
Although wind chill does not directly freeze objects, it rapidly speeds up cooling, making air temperatures below zero far more dangerous.
Air temperatures of between -2ºC and -30C being seen in many states today can stop car batteries working and even decrease battery life on electronics like mobile phones.
Water pipes and any liquid exposed to the cold can be frozen solid.
Video: Boiling water and extreme cold weather