Cold weather clothing selection
I came up with this list over the course of a few years of riding and have found it to be very helpful for me to select clothing for the ride in to work. Many people probably have different tolerances to heat/cold than I do, but its still a useful guideline to start with, just shift the temp ranges according to your preferences. Ideally you should be a bit chilly, but not cold as you start out. I typically don't ride in below freezing temps, (had enough of that as a paper boy in Wisconsin) so the list stops there.
60F and up Shorts, jersey, socks, riding gloves, glasses
55-60F Add arm warmers (or long sleeve jersey)
50-55F Add lycra tights
45-50F Add wind vest and long fingered gloves
40-45 Replace riding socks with wool socks, add 2nd layer (or warmer) long fingered gloves
32-40 Add 2nd layer of socks, 2nd layer of tights, 2nd layer of long sleeves, head band.
Above temps assume no heating from sun, no cooling from wind, and no rain. Adjust accordingly for those conditions.