Our winters are pretty mild in NC, so the coldest temperatures I have ridden in were the mid-teens. Usually I have one or two commutes each winter when morning temperatures are that cold, and I have been reasonably comfortable with my current gear. My biggest concern about riding in cold temps is dealing with mechanical problems. I do not look forward to fixing a flat in temps below freezing, and it's often dark outside when temps are that cold around here.

I am very comfortable riding in temps in the 20s and 30s, and actually prefer riding at those times to the hot, muggy weather we get here through most of the summer. It is much easier to dress for the cold than extreme heat and humidity. You can always add more layers of clothes but you can only take off so much, and high humidity makes you soaking wet within minutes of riding.

We get very little snow, sleet and ice in NC, and I don't ride in those conditions. I tried riding one day when we had about 6" of snow-sleet and only made it about 100 yards before I fell over. That was enough to convince me not to ride anymore. Black ice is especially treacherous, and we don't get enough snow and ice to justify putting studded tires on one of my bikes.