A: Chantal, you're right that children can get overheated and dehydrated more easily when they exercise in hot weather, especially when it's also humid. Younger children are more at risk than adolescents and adults for several reasons. They produce more heat when they exercise, for one, and they have larger skin surface relative to their small bodies, so they absorb more heat from the sun and air. Because they don't sweat as much, their bodies don't cool off as well, and they get so absorbed in their playing that they aren't aware that they need to rest, cool off and drink liquids.

The more dehydrated a child is, the easier it is for him to overheat. Children with certain medical conditions including obesity, diabetes, heart disease, cystic fibrosis and mental retardation are at even greater risk for overheating and dehydration.

Child health experts recommend the following precautions to prevent overheating and dehydration:

• Try to schedule outdoor activities before 10 a.m. and after 4 p.m.
• Dress your children in light-colored and lightweight clothes, and a hat with a brim. For protection against the sun's ultraviolet rays, be sure to apply sunscreen with a minimum of SPF 15 30 minutes before going outdoors, and reapply it every two hours. Also, encourage them to wear sunglasses with UVA and UVB protection.
• Make sure your children are well hydrated before, during and after outdoor activities. Beginning about 30 minutes before the activity, have them drink 4 to 8 ounces of liquid. During the activity, have them take breaks every 20 minutes to drink liquids: approximately 4 ounces for a younger child and 8 ounces for a teen-ager. They should drink whether or not they feel thirsty, since thirst isn't a good early warning sign of dehydration. Water, diluted fruit juices and sports drinks are all OK, but flavored drinks often help encourage children to drink more. After the activity is over, have them drink another 4 to 8 ounces.
• Have your children play in the shade as much as possible. If they play in the sun, encourage frequent breaks in the shade to cool off.
• If you see signs of heat exhaustion—flushed or pale sweaty skin, weakness, dizziness, headaches, nausea and vomiting—take your child to an air-conditioned or shaded area and help him cool off with sips of water, removing excess clothes, spraying water or rubbing ice on his skin and fanning it. If you see signs of heat stroke—red and hot dry skin, shallow rapid breathing, rapid pulse, seizures or loss of consciousness—call 911 or Emergency Medical Services immediately.