Your mother probably told you you’d catch your death of cold if you went outside without an adequate winter coat. She probably also said, “I told you so” when you caught a cold, whether it was soon after or the next month. I still find myself arguing that cold temperatures don’t cause the common cold or the flu, but those I argue with will never change their minds. Aaron Carroll of Healthcare Triage gives us the science behind these old myths about cold weather and your health. -via Laughing Squid
Same goes for alcohol. It doesn't warm you up, but it promotes circulation to your extremities both making you feel warmer, and reducing your chance of frostbite. Now, you might think that you're avoiding frostbite by risking hypothermia, but the statistics on actual incidents just do not show that alcohol increases risk of hypothermia, either. So alcohol causing hypothermia has much less evidence to support it, than the theory of being cold causing colds, does... In this light, his two positions are strangely contradictory.
http://www.theguardian.com/uk/2005/nov/14/science.health