um... if your arms aren't getting cold, you don't need to look for "winter biking clothing"

No, in general keeping your trunk warm will get you to a certain temp, but once you feel the need to put on a jacket, arm-warmers and legwarmers can be a handy way to keep your arms and legs warm but still adapt quickly if the day gets warmer. Plus they take little room in a jersey pocket, and are cheaper than buying a full jacket and tights. Downside - you have to have grippy bands of elastic+silicone around your upper arm/thigh. I prefer a longsleeved jersey unless I'm really pressed for carrying space.