Hmm,well that is crazy cold! I don't know about those temps and being out for hours but we had been -13 and it didn’t phase Rocky at all. He wasn’t out for hours in those temps but when he was , nothing seemed different to him?
We are way below freezing every night currently, Rocky is an indoor dog and if I let him out at night all he has to do is bark to come back in the house..it's been 6 years and he never barks to come back inside ,if I let him out night or day never!??
So I just throw a blanket out on the patio for him in case I fall asleep.