It's not frequent. Hasn't gotten that cold for a few years. We usually have a few nights at -30°F each winter.
Coldest I've ever had was -55°F when I was in a high camp in the Wind River Range in December. We had trouble keeping the stove lit, to melt snow for water and cook. Hunched up in our sleeping bags with our parkas , down vests, and all draped on top. Long night for sure.
I was younger (and tougher) then.
