I'm sure I'm not the only person who has reached for some whiskey (or any other booze for that matter) in an attempt to warm up on a cold night. Drinking it does give a warming sensation, but does it really raise our body temperature? Can bourbon replace your blanket when the heater's broken? Well, not exactly.
Booze actually reduces the body's core temperature when drunk in cold and even not so cold places. Let me explain - alcohol, chemically speaking, dilates the blood vessels upon drinking. When blood vessel are dilated, blood flows towards the surface of the skin, and warms the nerve endings there. While this gives the sensation of warmth, it actually makes us colder for two reasons: first, with warm blood near the surface of the skin, it is more easily absorbed by the colder outside air causing heat loss. Second, when there isn't alcohol in your system, your body draws blood to your organs when you're cold, which helps increase the core temperature. So, the dilation of vessels and the consequent blood flow away from the body's organs actually cools the body. It seems that the next time you are skiing, a flask of bourbon will more likely lead to hypothermia than to warmth.
Drinking booze also reduces the body's natural ability to shiver, which is one way your body creates warmth. Also, the quick warming sensation may be met by the natural reaction of sweating, and sweating during colder weather can drastically decrease your body temperature.
So, there you are - a science lesson. Bourbon may decrease body temps, but it certainly raises your spirits. Plus, if your barefoot and jacketless in northern Canada with no supplies but a fifth of Old Grandad, it's safe to say your troubles are far greater than those mentioned in this post.