Some girls will suffer for fashion. And thank the gods some of them will dress slutty in any weather.
Of course, in some cases they’re not suffering much. I’ve worn a kilt in decently cold weather (below freezing) and the damn thing was so warm that I had ball-sweat. Sure, my knees were cold, but my calves—clad in the appropriate wool socks—and thighs were toasty. I can easily see that between tights/nylons, long boots, and the right kind of skirt material those girls might not be cold at all.
Many nights I’ve gone to Boston in sub-zero temperatures for a night of clubbing. Nothing like standing in line for 20 minutes wearing what amounts to a bra, some fabric thrown over it, a miniskirt, panties and stilettos to thoroughly freeze you. But it’s worth it once you get inside and spend the rest of the night hot as hell from dancing. It’s uncomfortable, but preferable to the summer nights when you never get a chance to cool off from being hot all day.
I am now the opposite of freezing.
Well, go put on a miniskirt then! 
What if that makes me hotter? There are things I may not want to learn about myself. 
I was in the high school band, which had a sizable troupe of “Indianettes.” We did a half-time show at every football game. The band was in woolen uniforms, but the Indianettes wore silver lamé one-piece swimsuits and just-over-ankle-high tasseled white boots. Their pre-game treatment was heavy pancake makeup from hips to boots. Man, talk about frozen smiles!
I’m told that cold-weather marathoners coat their arms and legs with Atomic Balm, a hyper-liniment. :eek:
I think they can do it for the same reason that Highlanders could wear the kilt. Keeping the legs covered isn’t as important to overall warmth as protecting the torso & feet.
Also, there is the effect of what one is used to: someone who wears minis often is used to the draftiness already, & the switch of temperatures is less shocking; while someone who doesn’t wear minis regularly might find them uncomfortable in any temperature below 70. I also think that the sensitivity to cold that comes with age can kick in even in one’s twenties & worsen from there. So thirty-year-olds are colder than 25-year-olds, who are colder than teens.