Anything above freezing, no wind, and dry is fair game for the road rides. Although I have ridden the road in below freezing temps, icy, snowy conditions, I prefer to stay in the woods below these temps. The coldest its been while I've ridden is about 15 degrees. The trails get hard and fast when they are frozen. I like to hit the trails early in the winter mornings before temps get too warm and turn them to mud. Right now, in Baltimore MD its in the teens and wind chills are single digits close to zero.