The body needs a constant temperature of approximately 37°C to work properly. We adjust to changes in climate in two ways:
Behavioural, conscious reactions such as putting on more clothes or move our muscles.
Physiological, automatic (involuntary) reactions like changing the blood circulation, shivering or sweating.
The circulation of blood is concentrated to the vital organs at the core of the body and the head. Cold hands and feet are a first signal that you are starting to cool down: as your body is trying to prevent the temperature in your vital organs from falling, it is reducing blood flow to peripheral body parts. This raises the risk of frostbite.
Shivering is another important physiological reaction that occurs when the body temperature is dropping. With uncontrolled, quick muscle contractions the body tries to generate heat. When you have started to shiver it is hard to perform normal muscle work, and if the situation aggravates you risk hypothermia.
Sweating is a normal reaction when the body is overheated; it is the “cooler” of the body. In warm climates this is a necessary reaction to keep the balance of body temperature, but in cold climates it can be dangerous under unfortunate circumstances.
There is a Greenland saying that “if you sweat, you die”. This might be a little drastic, but it illustrates a point: when moisture enters the picture, frostbite often becomes an issue, even at temperatures above 0°C.
Water conducts heat 25-30 times better than air and rapidly transports energy away from the body. This is why sweat, snow and water are a threat to your well-being. This is particularly valid if you are on a long trek and are unable to dry your clothes and equipment at the end of the day.