Originally Posted by
Arcanum
At 20F, I might start being concerned with frostbite if I were going very far without ear covering. It depends on how long you're going to be out and how fast the effective wind speed while riding is.
My morning commute is about 10 miles and generally takes about 45 minutes. My route is hilly, so I reach speeds over 30 mph on several hills. I do have plenty of cycling caps that cover the top of my head and ears, so that is not the issue, but my face. I leave home at 6:30 am, so I am generally riding in the very coldest temperatures of the day.