The weather here is great we hardly ever get temperatures below 0ºC and when we do it is for a few days and it's usually dry.
When it rains temperature rises. I don't know probably around 10ºC will be the average temparature on a rainy day.
The most difficult thing for me is that I have to buy most things online, since the most advanced rain jacket on local bike shops is agu pooray 2000. Which isn't breathable at all with most of people using Windtex gear when it rains. But they are too cycling specific to use on my commute. As I have said above I am already regarded as a geek for biking to work, and I like to maintain a low profile, I'm just not willing to stop bike commuting due to others opinions.
I'm also a mountain biker and I've started commuting since polution really bugs me but also has a way to improve my mountain bike riding.
Nothing wrong with layering, last winter I used a TNF baselayer, a mamuth Polartech jacket and when it was really cold a fleece on top.
I need to get there dry especially the legs since I won't be changing pants. It is also nice to keep the baselayer on because that way I don't need a coat. I'm a teacher and every 90 minutes I go in and out of buildings.