I road from Northern California to Southern California this winter, and it rained on me about 2/3rds of my trip. Rain was pretty cold too. I don't recall ever being too cold to stand it, but my fingers more than anything faced the brunt of the rain. I was wishing that I had taken a pair of ski-gloves with me just for warmth. All I had was mild-weather rain gloves and summer gloves.
I just wore booties over my shoes, and that was enough for me. I think I had two pair of socks on my journey.
I've got to second the visor on the helmet. Without it, there would have been times where I couldn't see a thing.
I travel very light in general, and so my shelter was just a poncho tarp, but I'd wrap that over my clothes and it kept my sleeping clothes dry. I don't think I was ever seriously cold while riding, except for my hands, as I said.
Depending on where exactly you are going, there might be the opportunity to dry up in a bathroom. I actually spent about three or four nights in State Park bathrooms. Some even had an air-hand drier! It really makes a difference to go to sleep in a sheltered place after being rained on all day.