I've worn my 4-yd PV Bear Kilt out in -30C temps a few times. Was I warm? No, not particularly. Not that I'd have been any warmer wearing trousers. However, I was only out in the cold for 15-20 minutes at a time so it didn't bother me much. Now that I have a nice heavy tank to wear, it will be my "cold weather" kilt. That thing is probably warmer than most snowmobile or ski suits.

I define cold weather as anything colder than -18C, or 0F.