The heat is on - summer is in full swing, and it's easier and more convenient to have an outside workout than it is at any other time of the year. Whether you like to relax on the golf course or burn up some calories at a beach boot camp, staying cool is important to prevent heat-related illness. The exercise and air both have the effect of heating up your body and putting stress on your heart and lungs. And if you live in a humid climate, like the deep South, then your body may have trouble evaporating sweat and keeping you cool. Staying outside and making your natural cooling system work overtime can lead to heat cramps, heat exhaustion and ultimately, heatstroke. Prevent them by starting slowly, gradually allowing your body to get used to the heat and by drinking plenty of water, even when you don't feel thirsty.