I commute every day no matter what. I'm sure there are people out there biking in colder weather than me, which kind of keeps me motivated. To be honest cold doesn't bother me as much as a bad headwind or rain.
I ride in shorts till it's about 0C, or 32F, after that it's pants, important thing is staying warm while not getting wet/overheating. Check out the commuting forum for good clothing tips and cold weather riding. Layers are important, if fashion is of importance while biking in the cold your priorities are wrong.
Edit* 0C shorts, unless it's snowing/raining. I also try to warm up before heading out, which definitely helps.
Last edited by hardboiled718; 01-28-15 at 10:32 AM.