Children don't adapt as well as adults do to exercise in hot, humid weather. They produce more heat, sweat less and may be less likely to drink enough fluids during exercise — all of which increase their risk of dehydration.

Dehydration can cause mild to severe heat-related illnesses, such as heat cramps, heat exhaustion and heatstroke. Children who go out for football, soccer, cross-country and other sports that start in late summer may be at risk of developing dehydration and other heat-related illnesses.

Your child may be particularly vulnerable to dehydration and heat-related illness during summer workouts if he or she:

• Rarely exercises
• Is overweight or obese
• Has had a recent illness that caused vomiting or diarrhea
• Has had a previous heat-related illness
• Drinks caffeinated beverages or takes medications that can cause dehydration, such as antihistamines and diuretics

Most heat-related problems occur within the first few days of practice. Coaches should take it easy and gradually increase the amount of activity as the days progress. Young athletes may need up to 14 days to safely acclimate to the heat.

Sometimes, it's just too hot and muggy to go full throttle on the field. To determine when heat and humidity make strenuous exercise inadvisable for youngsters, coaches should use a device called a psychrometer to measure wet bulb globe temperature (WBGT).

The WBGT is the standard index of temperature and humidity combined. The American Academy of Pediatrics (AAP) has issued these guidelines for safe outdoor activity based on WBGT:

• WBGT below 75 F. All activities are allowed, but coaches should be alert for heat-related symptoms.
• WBGT between 75 F and 78.6 F. Children should take rest periods in the shade for long enough to cool off. They should also drink fluids every 15 minutes.
• WBGT between 79 F and 84 F. Children who haven't yet acclimated to the heat or who are at higher risk of dehydration and heat-related illnesses should stop playing and get out of the heat.
• WBGT 85 F and above. Cancel all outdoor athletic activities.

During hot and humid conditions, the AAP also recommends that coaches:

• Reduce the intensity of physical activity lasting more than 15 minutes
• Make children drink 5 ounces of water or a sports beverage every 15 to 20 minutes
• Make adolescents drink 9 ounces of water or a sports beverage every 15 to 20 minutes
• Enforce fluid consumption even if children aren't feeling thirsty

Thirst is not a good early-warning signal for dehydration. In fact, by the time your child is thirsty, he or she may already be dehydrated.

Other signs and symptoms of dehydration include:

• Feeling dizzy and lightheaded
• Having a dry or sticky mouth
• Producing less urine
• Producing dark yellow instead of clear or light yellow urine

Even mild dehydration can affect your child's athletic performance and make him or her lethargic and irritable. As dehydration worsens, it increases the risk of other heat-related illnesses such as heat cramps, heat exhaustion and heatstroke.

If your child plays sports in hot weather, you can reduce his or her risk of a heat-related illness by encouraging fluid consumption before, during and after practices and games. Also make sure your child's coach adjusts the intensity of practice depending on the WBGT on the field. Coaches should never hesitate to cancel games and practices when it's dangerously hot outside.