Try not to exercise in the hottest parts of the day. Early morning or evening is better.
Drink ample amounts of fluids. Thirst is not an accurate indicator of your need for fluid. When exercising in the hot and humid conditions, drink lots of water, but you may also want to add sports drinks into the mix to help balance electrolyte loss and provide carbohydrates that will help maintain blood glucose levels. Basketball on your driveway with the kids this summer can turn into a hot and sweaty exercise session for you and your kids. Keep in mind that sports drinks contain calories so stick to water if you are trying to lose weight. If you or your children are not fond of water pick up some of the new low calories sports drinks for both of you. I love the new Gatorade ad tag line: never underestimate the power of superior hydration. So drink, drink, drink to keep your body hydrated.
Wear as little clothing as possible to allow heat to escape to the environment.
Check the weather for heat, humidity, wind velocity and whether it is sunny or cloudy before you plan your outdoor activities.
Seek a cool environment if you start to cramp, get dizzy, feel faint or feel nauseous.