Man, does that bring back memories. Sub-zero temps are not uncommon in Denver, but one Winter ('89, maybe '90) we got down to -25 and stayed there for two weeks. The weird thing is that it's deceptively not really that uncomfortable. Yes, the air has a decided bite to it, and your breath condenses on your beard, and in your nose.
A scarf is a wonderful thing. And yes, glasses are an experience.
We were dressed for it, and as long as you were working and generating heat, it wasn't too bad.
But we has to be careful, because the last thing you want to do is start to sweat. You can go hypothermic pretty quick. I hate those wave shivers as your body ejects the deep chill.
I gotta stop. I'm getting cold just thinking about it.