Should you cut back clematis in winter?

They do in the North, where I garden. I'm not sure whether they freeze back or die back in warmer climates. Here in Iowa, I leave the old vines, though, for the new spring tendrils to climb up. ( They don't do well if you let them wander around on the ground; they get scraggly.) For clematis, remember, "cool feet, warm tops" and use lots of mulch at the roots.