a week ago, i did a 100 k ride. For much of the day the temp was in the 30's and a little in the 40's too. I wore 3 layers everywhere except my hands where I wore two. All the tights, woolen undergarments, fleece gloves, etc, etc came in handy. Oh wait, all i had on my head was one little wool hat under my helmet. I was just fine as long as I was moving.
Catrin, you need to just DO IT. it's not the cold, we can make excuses when it's (too) warm out as well.
I'm not suggesting you ride in snow or ice either. but if conditions are safe, you owe it to yourself to just get out and DO IT.