Gabe Mirkin, M.D.
In 1812, Napoleon attacked Russia with 453,000 men, but after he withdrew from Moscow, the harsh cold winter reduced his "Grande Armee" to fewer than 10,000 fighting men. The vast majority of Napoleon's soldiers were not killed by the Russians. They died of hypothermia, a severe drop in body temperature.
If you dress properly or exercise vigorously enough, it shouldn't happen to you. Your body sends you signals as your temperature starts to drop. With a one degree drop in temperature, your speech becomes slurred. This, in itself, is not dangerous, and occurs when people stay out in temperatures below 35 degrees, but it serves as a warning that you are losing more heat than your body is producing. To protect yourself, you can produce more heat by exercising harder or you can conserve heat by adding more layers of clothes.
With a drop of three degrees, you'll find it difficult to coordinate your fingers. Seek shelter immediately. When your temperature drops five degrees, you won't be able to walk and you'll stumble and fall and not be able to get up. Then you may not be able to get out of the cold and your body temperature can continue to drop rapidly and you can die. If your clothes are wet, your temperature will drop even faster. Take the warning signals seriously; if you have slurred speech or difficulty using your hands, take action or you may not get another chance.