It was still pretty chilly this spring when I started commuting and since I was still trying out the commuting thing, I just dove in the closet for things I had from other sports. Every now and then I'm sampling a new activity, so I like to have things that will work in multiple situations.

A base layer + lightweight fleece + a light rain shell was enought to keep me warm, although I was often a bit moist by the time I got to the office. For visibility, I wear a screaming yellow PI vest. My rain shell sticks out all funny under the vest, since it's not as fitted, but it gets the job done. Since I don't know whether I'll like winter commuting, I'll probably keep using this ensemble until I know how committed I am to it.

I figure I'll have to reach a certain level of discomfort with the weather and my current gear to know what I'll need or what will work for me.

Good luck with the schedule constraints!