Make sure that you don't overly cool the patient as their body's temperature regulation system has failed. Evacuate as soon as possible. Mainly a problem in the spring and summer, lightning poses a serious threat to people in the backcountry. The best way to avoid being struck is to avoid ridges, open spaces and caves during lightning storms. If you are caught in an open area or above treeline, make sure you are far away from any metal objects, put an insulated pad between you and the ground and stay as low as possible.
More Dehydration is quite a simple problem to prevent.
Just make sure you are packing enough water for the conditions you're in, drink before you're thirsty, and have an idea of where you will be able to find more. Roughly speaking, the average adult requires a minimum of 2-3 quarts a day, more if you are in the desert or cold conditions or at altitude. Dehydration can lead to frostbite, heat stroke, headache, bad judgement and, in extreme cases, death. The best way to prevent giardia is to filter or purify all water before drinking it regardless of how clear it looks. Treat water by using a filter that traps particles larger than 0.2 microns, a chemical treatment according to its instructions or by boiling water for at least five minutes.