Strenuous work outdoors on a hot, humid day can quickly take its toll on the body. In addition to the heat absorbed from the sun, muscles will generate heat as they flex. This added heat will help raise the body's temperature even higher. It takes about 15 days for the average person to become acclimated to the hot weather. Start with smaller jobs for brief periods early in the season, then work up to larger tasks.
It's also important to wear the right clothes. Long pants, a long-sleeved shirt, and especially a wide-brimmed hat will protect you from the sun's intense rays, as more than 50% of the body's heat is absorbed or dissipated through the head. Cotton fabrics are cooler than synthetics as they allow more air circulation between the fibers. Dark fabrics block the sun's rays better than light ones, but they absorb more heat, so it's better to wear light-colored fabrics.
Drink about 16 ounces of fluids 2 hours before starting work, and continue drinking as you feel thirsty. Avoid ice-cold fluids when you're hot; they can shock the stomach muscles and cause heat cramps.
Listen to your body. Know the symptoms of heat exhaustion and heatstroke. Heat exhaustion starts with extreme thirst, then progresses into nausea, dizziness, vomiting, headaches and heat cramps. If left unchecked, it will lead to heatstroke.