I've been out in -7 degree weather in North Dakota. It's so cold that every little piece of exposed skin just HURTS. Luckily, I only had to be outside for about 10 minutes while it was that cold.
i can work all day in colder weather, forty to fifty five is great....anything over that, i call hot..
minus thirty actual, plus wind of twenty mph is the worst i have been in..too much.. but still better than sweating your nuts off ....