Prosody

You have to play around with what you wear. If you overdress, you're likely to get very cold toward the end of a ride because you'll be drenched with sweat. If you underdress, you'll be miserably cold the entire ride. A good measure for starting is that, at the beginning of a ride, you should be somewhat cold so that the heat you create warms you up. If you are warm when you start, you have overdressed. If you don't warm up after ten or fifteen minutes, you have underdressed. Last winter here in Missouri I'd wear a base layer, a long sleeve jersey, a wind jacket, my cycling shorts, knee warmers, thin tights, head covering under the helmet, warm cycling gloves. At 35 degrees F. that would keep me warm enough. At 40 degrees, I'd be overdressed. I imagine individual differences will play a role in just how anyone dresses.

I've read several places that you should avoid intense effort during winter cycling and concentrate instead on building mileage. I guess that's because any intense effort is going to leave you sweaty and cold.