Everyone answered your question, but it reminded me so I thought I'd share in case you wanted some other evil thing to do to your characters.
I've been in -35 temps (btw, past a certain point, C and F equal out), and yes your nose hairs get freezy and stuff, but the weirdest, most notable thing I remember was learning that you can't so much breathe through your mouth.
I was in the airport, with some people, and the airport was quite warm and stuffy, so a few of us said we wanted to go get some air while we waited for our bags to be offloaded. The person who had spent time in that kind of weather gleefully gestured us toward the door and watched.
We went out, took a deep 'ahh,' breath with open mouths, and promptly started choking. Your lungs aren't, it turns out, stupid.
Your body won't let air that cold into your lungs without warming it first. Your throat will simply close and cut off the cold air, so you can't damage stuff. That's nice, except if you have no idea it's going to happen, or what is happening, all you know is you suddenly can't inhale and have no air, which is sort of, let's say, distressing.
The person who was accustomed to the weather I can still picture, sitting inside, with an amused grin, watching the little cluster of us, who hadn't made it more than two feet outside the doors, doubled over, clutching our throats, panicking and scrabbling for the doors to try to get back in. We managed to stagger forward to trigger the doors, basically fall inside and a few seconds later could breathe again, because the air was warmer.