Visitors to New Mexico face several unique health concerns. First and foremost are the simple environmental hazards of dehydration, sunburn, and altitude sickness. The desert climate, glaring sun, and thin ozone layer conspire to fry your skin to a crisp and drain you of all moisture. (On the plus side, sweat evaporates immediately.) Apply SPF 30 sunscreen daily, even in winter, and try to drink at least a couple of liters of water a day, whether you feel thirsty or not; remember to ask for water in restaurants—it’s frequently brought only on demand to cut down on waste. After you start feeling thirsty, you’re already seriously dehydrated and at risk of further bad effects: headaches, nausea, and dizziness, all of which can become full-blown, life-threatening heatstroke if left untreated. It doesn’t even take serious exertion—just lack of water and very hot sun—to develop heatstroke, so if you’re feeling at all woozy or cranky (another common symptom of a lack of water), head for shade and sip a cold drink. Gatorade or a similar electrolyte-replacement drink is a good option, but avoid caffeine- and sugar-laden soft drinks or iced coffee.

Staying hydrated will also help stave off the effects of the high elevation, which most visitors will not be used to. The mildest reaction to being 7,000 feet or more above sea level is simple lethargy or lightheadedness—you will probably sleep long and soundly on your first night in New Mexico. Some people do have more severe reactions, such as a piercing headache or intense nausea, especially if they engage in strenuous physical activity. Unfortunately, there’s no good way to judge how your body will react, so give yourself a few days to acclimate, with a light schedule and plenty of time to sleep.

More obscure hazards include West Nile virus (wear a DEET-based repellent if you’re along the river in the summer); hantavirus, an extremely rare pulmonary ailment transmitted by rodents; and the even rarer bubonic plague (a.k.a. The Black Death), the very same disease that killed millions of Europeans in the Middle Ages. Only a case or two of the plague crops up every year, and it’s easily treated if diagnosed early. Lyme disease is so far nonexistent, as deer ticks do not flourish in the mountains.

If you’ll be spending a lot of time hiking, take precautions against giardiasis and other waterborne ailments by boiling your water or treating it with iodine—even the clearest mountain waterways may have been tainted by cows upstream. Snake bites are also a small hazard in the wild, so wear boots that cover your ankles, stay on trails, and keep your hands and feet out of odd holes and cracks between rocks. Only the Western diamondback is aggressive when disturbed; other snakes will bolt, and will certainly not bite if you simply back away quietly.

And the general outdoor safety rules apply: Don’t hike by yourself, always register with the ranger station when heading out overnight, and let friends know where you’re going and when you’ll be back. Pack a good topographical map and a compass or GPS device; people manage to get lost even when hiking in the foothills, and if you’re at all dehydrated or dizzy from the altitude, any disorientation can be magnified to a disastrous degree. Also pack layers of clothing, and be prepared for cold snaps and snow at higher elevations even in the summer.