Peru’s snow-covered mountains, highlands, and even cloud forests have plenty of cold, rainy days, conditions in which hypothermia is most likely to occur. Watch yourself and those around you for early signs of hypothermia, which include shivering, crankiness, exhaustion, clammy skin, and loss of fine coordination. In more advanced hypothermia the person stumbles, slurs his or her speech, acts irrationally, and eventually becomes unconscious, a state doctors refer to as the “metabolic ice box.”

The key to preventing hypothermia is being prepared for the elements, and that starts with clothing. When you go for a hike, pack plenty of different layers in a plastic bag. Remember that cotton is great for evaporating sweat and cooling down on a hot day, but actually works against you in wet, cold weather. Artificial fibers like fleece or polypropylene work when wet because they wick water away from your body. Wool is another good choice because it insulates even when wet. And a waterproof poncho or a Gore-Tex jacket will help keep you dry. Having a lot of food and water is also important, and in demanding conditions you and everyone you are with should be fueling up constantly.

The key to avoiding hypothermia is catching it early. If you or someone in your group is shivering or having a hard time zipping up a jacket, take action immediately. In mild hypothermia, the body is still trying to warm itself, and all you have to do is support that process. Feed the person water and a variety of foods, from fast-burning chocolate to bread and cheese. Have them do vigorous exercises like squatting and standing over and over, or swinging their arms around like a windmill. If the person remains cold, set up a tent and put him or her in a sleeping bag with hot-water bottles. Monitor the person carefully until body temperature returns to normal. A person who was on the edge of hypothermia one day is more susceptible the next, so allow for at least a day or two of rest and recuperation.