One thing I have noticed is that after a couple of months of winter riding, your body adjusts by sweating less for a given level of effort. It's been just above zero the past couple of weeks, and I'm now riding around in lycra shorts and one top layer, not quite windproof, with no discomfort at all. Hairy legs help. I'm thin... don't know if being fat helps.
A couple of days ago I did an experiment... it was zero, humidity around 90%, and I decided to ride home in that to see what got cold first. Usually when it gets close to zero I put on some long tights and my Frosty Boy (
www.groundeffect.co.nz), although I usually end up too hot after 15min, especially around the shoulders.
It really was zero, there was ice forming. In fact, I went **** skating on some of it. Humidity was close to 100% on the riverbank, and you can feel the difference. It's like the hand of death.
I was wearing overshoes (thin hiking undersocks) and proper winter gloves... I don't mess around with hands and feet.
What got cold was legs (at first), fingertips (end of ride), insides of elbows, the tops of the front insides of my thighs, neck (at first), teeth (this happens if you go hard enough to open your mouth, which you have to to keep the rest of you warm).
By the time I got home I was warm, except for those fingertips.
Don't overdress. You will get used to it.