Being from Sweden, Leif seems to be able to handle cold much better than most people. Even in the winter, I rarely see him wear pants unless we have to go out someplace or it's below 0. He rarely even wears a jacket, insisting he's fine in a sweatshirt. This is also the same guy who constantly complains the bedroom is a sauna, even if the window is open in the winter. I'll add as well, that when he's gone on a business trip and it's just me and the dogs in the bed (the dogs only sleep in the bed when he's gone), and I have the winter closed, it's perfectly comfortable, so I'm guessing he just radiates a lot of heat.
The funniest thing though I see him do every winter is shovel the driveway while wearing shorts and sneakers. It just feels wrong.