Summer heat waves can be dangerous. Older people are at the highest risk. People normally cool their bodies by sweating, but under some conditions, sweating isn't enough. Very high body temperatures may damage the brain or other vital organs. Some conditions that can limit the ability to regulate temperature include old age, obesity, fever, dehydration, heart disease, poor circulation, sunburn, and drug and alcohol use. Summertime activity, whether on the playing field or the construction site, must be done in a way to aid the body's cooling mechanisms and prevent heat-related illness.