Family has property in far north. just a hop, and not even a skip and jump, from Canada. One thing always pushed is to keep the face covered. Peace mentioned the frost bite. There is also the need to keep you mouth covered when you hit the temps that far below zero.
I can't imagine how insane 70 below would be. Seen more than 40 below and it was just flat out dangerous.
Someone asked when does cold stop feeling colder, I would agree that some up there have more that reached that point. After that, it is just how the body responds.
I think they have had over 10 people die in the past two days up there. Some poor guy was found frozen to death in his garage.
When it gets over 105 here, it is miserable times 10. I was in 114 this past summer in central Texas. Horrible, but I don't think it could ever compare to the extremes of 30 below zero or lower. At that point, you are in a home, heater going, and it still feels cooler than you want.