Peru’s tropical sun and its climate extremes, from searing desert to steamy jungle, can be dangerous for those who are unaccustomed to them. Like hypothermia, heat exhaustion is caused by environmental conditions that knock the body temperature out of whack. And like hypothermia, heat-related illnesses can be deadly if not treated in time.

People suffering from heat exhaustion usually have been sweating profusely and have become dehydrated, which causes the person to have a headache. The skin appears pale and the person may vomit or feel dizzy after standing. The heart rate is elevated and, at first glance, the person appears to have the flu.

It is vital to take care of the problem before it gets worse. Find a shady spot—or create one with clothing—and give the person plenty of water, preferably mixed with electrolytes or at least a pinch or two of salt. Place damp, cool cloths on the person’s face and back. Allow them to sleep if they feel drowsy. Another side effect of dehydration is painful heat cramps, which can be relieved by hydration and massage.

People are more prone to heat exhaustion when they are dehydrated, overweight, unaccustomed to a sunny or humid climate, and either very young or old. Taking it easy and drinking plenty of water is the best way to avoid heat exhaustion. Wearing a wide-brimmed hat and loose cotton clothing that covers the body is also important, along with applying plenty of sunscreen. If you exert yourself on a hot day, remember that you should be drinking 2–4 liters of water per day.