In hot and dry areas

Your body constantly produces heat when working, and on hot days heat from outside adds to it: direct sun, light reflected from bright ground and hot air. To avoid overheating, the body gets rid of heat mainly by evaporating sweat. In dry air this works well – so well that you often do not even notice the sweat because it evaporates at once. That is exactly what makes it treacherous: you lose a lot of water without realising.

If more heat comes in than the body can get rid of, body temperature rises. At first there is often exhaustion, headache, dizziness and nausea. If the load is not reduced, this can turn into heatstroke, where the body can no longer regulate its temperature. That is life-threatening.

Dry regions have a second side too: at night it can cool down sharply there, because dry air and a cloudless sky let heat escape quickly. And rain, when it comes, often falls as a violent thunderstorm downpour. The hard, dry ground barely absorbs the water; it collects in channels and riverbeds and can arrive as a flash flood even where not a drop is falling.

Water is planned, not hoped for. How much someone needs depends on heat, exertion, body and clothing, so there is no fixed number that fits everyone. Plan generously, include a reserve and rely only on water points that are known and currently confirmed. A spring on an old map may have dried up long ago. If there is no reliable way to refill, turn back before half the water is used.

Drink the water instead of saving it in your pack. Water in the bottle does not protect you – only water you have drunk does. Drink regularly, not only when you are thirsty, and when sweating heavily eat something salty too, because salt is lost with sweat. Very dark urine or rarely needing to pee are simple signs that you are drinking too little.

Time of day is your second tool. Many people in hot countries rest during the midday heat, and for good reason. Starting early and seeking shade in the hottest hours saves water and strength. Clothing helps too: loose, light-coloured, long-sleeved, with a wide-brimmed hat and sunglasses. It keeps direct sun off your skin while sweat can still evaporate underneath.

Heatstroke is an emergency. Warning signs are confusion, odd behaviour, impaired consciousness, seizures or a very high body temperature. Then call the local emergency number at once (112 in the EU), move the person into the shade, loosen tight clothing and cool them, for example with water and moving air. Even early signs such as severe exhaustion, headache or nausea are a signal to stop exerting yourself and get into the shade.

Dry riverbeds, also called wadis or washes, and narrow canyons are no place to rest or camp when thunderstorms threaten. The water can come from a storm far away that you cannot even see. Choose raised camp sites away from drainage channels, and before trips into canyons check the forecast for the whole region.

If your vehicle breaks down in remote terrain, it is usually better to stay with it. It gives shade, is much easier to spot from the air and from afar than a single person, and water and gear can be stored in it. Leaving your route with someone beforehand means you are searched for and found sooner.

A common misconception is that you should “ration” water for as long as possible to make it last. Anyone who drinks too little becomes weak and unfocused sooner and is more prone to heat illness. It is wiser to reduce exertion and heat – staying in the shade and moving in the cool hours – and to drink the water you have when your body needs it.

Desert nights can be surprisingly cold. A warm layer and a sleeping bag therefore belong in the pack despite the daytime heat. Also think of sun protection for lips and eyes, because sun and dry wind irritate them strongly.

Deserts are not the only hot, dry places. Steppes, Mediterranean summers and heatwaves at home follow the same rules: water, shade, time of day. Anyone in a group at higher heat risk – because of age, existing conditions or medication, for example – should discuss trips in the heat with a doctor beforehand.