Take care when exercising in the heat

Fuel yourself. Drink water before, during and after exercise. Aim for 5-10 ounces every 15 minutes while working out, says Dr. Eliot Young, a sports medicine specialist at Christus Santa Rosa and medical director for the Rock 'n' Roll San Antonio Marathon.

Dress right. Wear light, loose clothing. Avoid cotton; instead, choose fabric that wicks moisture from the skin. Wear a cap or visor to shade your face and cool your head. Cyclists should wear a vented bike helmet to catch breezes. Don't forget the sunscreen -- getting sunburned hurts the body's ability to cool down.

Acclimate. If you're just starting to exercise in serious heat, don't go whole-hog right away.

Be safe. Obese people, people taking diuretics, those older than 65 and people with certain chronic illnesses are at greater risk for heat-related illnesses. Pregnant women should avoid extreme heat in all trimesters.

Train on cooler surfaces. "Heat from a grassy area is less than heat from concrete," Young says. "White concrete is better than black asphalt."

Pay attention to your body. Unusual fatigue and headache are early signs of dehydration; decreased sweat production, dizziness, nausea and cramps also signal danger.