Peace, my son is a cable technician and last week the temps here in MN went to -15 below during the day. My son called in the morning and said slowly, "-117, two men unconscious..." And once our laughter had died down I heard him jogging to his truck as he said, "Hang on, I have to phaser some rocks to get some heat in my truck."
What befuddles me about that scene is... why didn't they send down the shuttle craft? I know, I know, it was before they invented the thing, so why didn't Sulu make a tent around some rocks, close it off and then heat the rocks? Spock told him 'survival procedures'... and cuddling in his neoprene blanket sufficed?