The Associated Press reports during extreme heat, adequate fluids are especially important because dehydration can be a life-threatening problem. Children, older adults, athletes, adults and people who work or are physically active outside for extended periods of time are particularly at risk for dehydration.

Signs of dehydration include thirst, dry mouth and flushed skin. A dehydrated person may have a headache or feel weak and confused. The urine may be amber colored and the urine volume may be unusually low.

Recognizing signs of dehydration early is critical because serious dehydration can cause coma or death. A loss of only 5 percent of body water can result in some signs of heat exhaustion. A loss of 10 percent of body water can lead to heat stroke and circulatory collapse.

Most people usually underestimate how much fluid they need to replace water lost due to prolonged exposure to extreme heat. Unfortunately, thirst is not an indicator of fluid need because the onset of thirst lags behind the body’s need for water.

Normal fluid needs for adults are at least six to eight cups each day. However, extra fluid is required for prolonged exposure to heat. For outside activities lasting less than an hour, an extra one to two cups of water should be enough. For extended outside activity, additional fluid needs to be consumed before, during and after time outdoors.

Guidelines for fluid intake for extended outside activities include two to three cups of fluid about two hours before activity and an additional 1-2 cups of fluid about 15 minutes before the activity. Small amounts of fluid, about six to eight ounces, should be consumed about every 15 to 20 minutes or two to three cups every hour during the activity.

After outside activity, fluid should be consumed to replace weight loss. A tip for replacing water loss is to weigh before and after outside activity. A general rule is two cups of fluid are needed to replace every pound lost.

For activities lasting less than an hour, plain, cool water is best for replacing body water because it can be absorbed quickly. Juices, soft drinks and other liquids containing more than 8 percent sugar may cause stomach cramps and diarrhea. Most sport drinks contain about 7 percent sugar, which is about half the amount of sugar in regular soft drinks.