As Southerners we don't see that weather very often. Our local low of 3° and crazy wind chills wasn't a record by any means, and it is not extreme compared to the northern climates, but it's so unusual that it's been decades since the last time. If you commuted in it, and you're a seasoned commuter with none of this zub-zero experience, what did you learn that was surprising?
I figured it would just be like the usual cold rides, only more so. I knew already that cold weather generally makes you slower, and just generally feels like something is draining your accustomed power away. But when it's a LOT colder, there was a LOT more resistance and fatigue and that surprised me. I mean my speed was down to almost half and I wasn't slacking.
You can add enough layers that you'll still arrive with sweat-drenched base layers, regardless of the temperature. That shouldn't have surprised me, but it did.
And finally, something changes with your position on the bike or your motions. Or maybe I tensed up, but whatever it was I'm still recovering from various muscle aches and my joints are randomly complaining. I didn't expect that either.
So, what else?