Any time temps get above 90 degrees with 60+% humidity, a person can get in real trouble. The environment is such that even if the body isn't dehydrated yet, sweat won't evaporate fast enough to cool the body. To avoid this, wear loose light colored clothing and a hat, drink at least 8oz of water an hour, an occasional sports drink can help replenishment electrolytes, stay away from caffeinated or alcoholic drinks. Be aware that diabetics, the over weight, some medications and blood pressure problems among others can make one susceptible to heat exhaustion.
Heat exhaustion can be brought on by both lack of electrolytes or water in the system. If you feel it coming on, get to a cool place, slam water and get help. Heat exhaustion can develop into heat stroke, which can cause serious damage to one's body, including permanent brain damage or death.
