I rode outside for the first time in my life in December, in the Chicago area... I know others do it, but I had not dared before. The temperature was just under 40, with a windchill ~29 degrees, some wind. I managed not to freeze my fingers and toes in a little over 2 hours 20min. I will add that to my total, even though it was outdoors!
It feels very different to ride with the cold, dry air; very tiring but fun to be outside for a change. Maybe I will dare again tomorrow. Brrr.