When I started winter commuting two years ago I read a bunch of threads here and at Cascade.org, and did a bunch of experimentation. I have found (no surprise here) that layering is really key - what feels comfy at 35 degrees and rainy is not at all the right stuff at 45 degrees and dry.
My winter outfit is:
- Fenders
- ShowersPass Elite rain jacket, with hood
- Rain cover over helmet
- Skullcap if it's cold
- Baseball cap under helmet if it's raining hard
- Most days if it's under 45 degrees I wear Specialized BG Defroster Mountain Bike boots. They are much handier for me than dealing with booties.
- Pants are cycling tights - warmer ones if it's cold out, plain ones if it's cold. If it's *really* cold, I wear a pair of jogging/exercise pants over cycling tights.
- For gloves I wear full-finger Specialized cycling gloves; if it's cold I wear glove liners under them. I have found gloves + liners better than thick gloves.
For my upper body I've found it doesn't really matter what I wear under my Showers Pass jacket as long as I'm warm. I mix and match all kinds of stuff under my jacket - cycling gear, wicking t-shirts, some old ski turtlenecks. Usually I'm wearing a short-sleeve synthetic undershirt under some kind of long-sleeved jersey, but it could be more or less depending on the temperature.