Pedal enough to keep up a sweat and you will be fine. What you are wearing becomes more of an issue when you stop. I x-country skied one day in -35 F (that is minus). All I wore was a sweat shirt and sweat pants with a set of U.S. Military surplus EWCS light weight fleece under suit. No problem at all while heated up and sweating. Potential big problem when stopped for more than a few minutes. Working up a sweat, and more importantly wearing clothing that wicks that sweat away from your body (it freezes when you stop and drives down body temperature quickly) will keep you warm.