It's kinda hard to associate you and warmth. [ There is an awkward moment in which he acknowledges that he wants to get closer to Cas in order to get warmer but that would mean touching him more than he is doing now. ]

Just so you know, I'm not this sensitive to cold, it's only that I'm... not... wearing clothes. And this cabin is letting a lot of air in. [ Justifying it to himself more than Cas. ]