I didn't ride on the 9-degree morning but did ride when it was 15 F. The main issue I noticed was my hands and feet getting cold, which was the main reason why I didn't ride when it was 9 F. Surprisingly I didn't sweat hardly at all at 15 degrees, even with an extra layer of clothes. I attribute that to the Showers Pass Elite jacket I was wearing for my outer layer because it is very breathable.

I have noticed differences in bike fit since the weather got cold in November but hadn't really attributed it to the weather. My reach seems to have shrunk with the cold and my handlebars all feel a little too far away. The main difference that I notice with the cold is slower speeds, and my pace seems to drop in a direct relationship with the temperature declines. It's often windier here in winter as well, so that is another factor affecting speed in addition to the denser air, tighter muscles and bulkier clothes.