I'd love to see any research on whether humans can "toughen up" against cold or otherwise increase climate tolerance. Can't say I have, but I think frequent riding at the very least makes you hardier psychologically. Above 30 degrees and I ride - and I am otherwise a *very cold* person in winter, subsisting between every possible external heat source (sweaters, tea, and cuddling ranking highest). But I'm convinced that morning riding warms the blood all day. As for clothing...always dress for the second mile.