Drink enough water to stay safe outside.
The best way to prevent dehydration is to consciously drink water slowly over several hours before intense exercise. During periods of heavy exercise you should drink about one quart per hour. If your urine is clear and copious, then you know you are well-hydrated.
When the weather is brutally hot and your body sweats profusely, water by itself is not enough. Sweating out salts diminishes your body's ability to regulate liquids. Munching on GORP (good old raisins and peanuts, aka trail mix) or another salty snack can help avoid this problem, but sometimes you need a little extra help. Sports drinks containing salts, potassium and electrolytes are effective at staving off this problem, but be wary of drinking too much since they often contain large amounts of sugar. In a quick pinch, a dash of salt and sugar can be added to a water bottle for similar results.
When hiking with children check their water bottles periodically to ensure that they are taking the time to consume enough water. While having fun outdoors, children will frequently not want to stop to drink or eat even though they are thirsty and hungry.
Avoid drinking caffeinated beverages – they act as diuretics, causing you to urinate more often.
Despite the fact that sweating isn't as obvious in the winter or in dry climates, hydration can be more important in the colder months than the warmer months. Cold, dry air strips the water from our bodies faster than warm humid air, necessitating the consumption of more water during a winter hike. Keep your tightly-sealed water bottle inside your coat to help keep the water from freezing.
One of the earliest symptoms of dehydration is one that is the most often overlooked: a headache. If ignored, the victim is subject to temperature related illnesses such as heat stroke and hypothermia. Dehydration can cause hikers to become confused and disoriented, which if hiking alone, can quickly lead an otherwise capable hiker to become lost.
Dehydration victims often exhibit a lack of appetite from nausea and dizziness.
Be watchful of your urine color. If your urine is dark and you've already got a headache, chances are you are well on your way to dehydration.
Depending on the severity of the dehydration, it can usually be cured with some water and relaxation. A dehydration victim should not exert themselves for several hours at the very least and should be consistently sipping on water mixed with a dash of salt and sugar. Lying in a cool, shady spot, with their feet elevated is also helpful.
Of course, prevention is the best treatment for dehydration. Dehydration is a gateway illness to heat exhaustion, heat stroke, and hypothermia, and can provoke shock from physical injury.
If suffering from severe dehydration seek medical attention as soon as possible.
Source: American Hiking Society. Please visit the AHS Website for more information.