I live in southern Ontario and commute on foot year-round. There's no weather that appropriate outerwear can't handle.
I had a ruptured disk and a spinal fusion a few years ago that went really well.... and I'm a little paranoid about keeping it that way!
I now live in Vancouver and despite temperature it gets damp enough that movement without sweating is well nigh impossible. Good thing I work at a pool and don't give a damn.
Either way cycling is still better.