I haven't had any problem yet. One ride last weekend I did was up a mountain to a ski area in Anchorage, Alaska. It was snowing at the top, about 25 F. I had a long sleeve, skin tight riding jersey underneath, and a slightly heavier (but still light) riding jersey/jacket on the outside. I also wore long pants. The fabric in pants and jacket is nylon, polyester, lycra, spandex, blend. I wore two pairs of socks designed for cross country skiing: the underneath one is very thin and designed to wick the moisture away from the foot, the one on the outside is I think a wool blend, also very thin. I was very comfortable on the way up, 20+ % grade and the way down (high speed). I unzipped the jacket to let the cool air in on the way up, and zipped it back up when I went down. The trick is to wear layers in the arctic; even thin layers are better than trying to get it all with one. I ride at as cold as 45 below F, but then I get a bit too bulky to really call it a decent workout. The breakpoint seems to be around 20 to 25 below when you really start to notice the cold, and the legs seem like they just won't get going.
20 to 25 below... you are not human. that is crazy cold. honestly, my breaking point is +30. then i take it inside on the trainer, which is very boring.
