Sierra South. Mike White

      This may feel cool and refreshing, but it’s advisable to filter or boil water before drinking it.

      Hypothermia: Hypothermia refers to subnormal body temperature. More hikers die from hypothermia than from any other single cause. Caused by exposure to cold, often intensified by wet, wind, and weariness, the first symptoms of hypothermia are uncontrollable shivering and imperfect motor coordination. These are rapidly followed by loss of judgment, so that you yourself cannot make the decisions to protect your own life. Death by “exposure” is death by hypothermia.

      To prevent hypothermia, stay warm: Carry wind- and rain-protective clothing, and put it on as soon as you feel chilly. Stay dry: Carry or wear wool or a suitable synthetic (not cotton) against your skin, and bring raingear, even for a short hike on an apparently sunny day. If weather conditions threaten and you are inadequately prepared, flee or hunker down.

      Treat shivering at once: Get the victim out of the wind and wet, replace all wet clothes with dry ones, put him or her in a sleeping bag, and give him or her warm drinks. If the shivering is severe and accompanied by other symptoms, strip him or her and yourself (and a third party if possible), and warm him or her with your own bodies, tightly wrapped in a dry sleeping bag.

      Lightning: Although the odds of being struck are very small, almost everyone who goes to the mountains thinks about it. If a thunderstorm comes upon you, avoid exposed places—mountain peaks, mountain ridges, open fields, a boat on a lake—and also avoid small caves and rock overhangs. The safest place is an opening or a clump of small trees in a forest.

      The best body stance is one that minimizes the area your body touches the ground. You should drop to your knees and put your hands on your knees. This is because the more area your body covers, the more chance that ground currents will pass through it. Also make sure to get all metal—such as frame packs, tent poles, etc.—away from you.

      If you get struck by lightning, there isn’t much you can do except pray that someone in your party is adept at CPR—or at least adept at artificial respiration if your breathing has stopped but not your heart. It may take hours for a victim to resume breathing on his or her own. If your companions are victims, attend first to those who are not moving. Those who are rolling around and moaning are at least breathing. Finally, a victim who lives should be evacuated to a hospital, because other problems often develop in lightning victims.

Wildlife Hazards

      Rattlesnakes: They occur at lower elevations (they are rarely seen above 7000 feet but have been seen up to 9000 feet) in a range of habitats, but most commonly near riverbeds and streams. Their bite is rarely fatal to an adult, but a bite that carries venom may still cause extensive tissue damage.

      If you are bitten, get to a hospital as soon as possible. There is no substitute for proper medical treatment.

      Some people carry a snakebite kit such as Sawyer’s extractor when traveling in remote areas far from help and where snake encounters are more likely: below 6000 feet along a watercourse. This kit is somewhat effective if used properly within 30 minutes after the bite—but it’s still no substitute for hospital care.

      Better yet, don’t get bitten: Watch where you place your hands and feet; listen for the rattle. If you hear a snake rattle, stand still long enough to determine where it is, then leave in the opposite direction.