I commuted one winter when the temperature didn't get above zero F for an entire month. I only really had trouble on the 2 days it was -20F. There is a cutoff in there that makes frostbite a lot easier to occur. Now that I've moved to a little warmer area, somewhere around 5-10F is probably my limit. I keep thinking about putting bar mitts on my commuter, but I haven't done it yet. I have trouble with my hands getting too cold. There is one spot on my commute that is really exposed to the wind, and I haven't successfully found gloves that will keep my hands warm.