Blistering summer heat waves can be not only extremely uncomfortable, but even deadly, as Europe learned during the summer of 2003.
History shows that heat waves are deadliest in large cities that rarely experience hot weather, with the elderly and those in poor health in the greatest danger.
In recent years, scientists have learned that a day's highest temperature is not the best measure of the danger of heat waves. Unrelenting heat that doesn't allow people to rest at night is responsible for the deaths of many elderly and ill people.
The elderly and ill aren't the only people that heat kills. It also kills healthy young people, usually because they do not recognize the dangers of exercising in hot weather, especially hot, humid weather.
When heat and humidity combine to slow evaporation of sweat from the body, outdoor exercise becomes dangerous even for those in good shape. Key rules for coping with heat are to drink plenty of water to avoid dehydration and to slow down and cool off when feeling fatigued, a headache, a high pulse rate or shallow breathing. Overheating can cause serious, even life-threatening conditions such as heat stroke.
Dangers of Heat Include
Heat cramps: Exercising in hot weather can lead to muscle cramps, especially in the legs, because of brief imbalances in body salts. Cramps become less frequent as a person becomes used to the heat.
Heatstroke: In some cases extreme heat can upset the body's thermostat, causing body temperature to rise to 105 degrees or higher. Symptoms are lethargy, confusion and unconsciousness. Even a suspicion that someone might be suffering from heatstroke requires immediate medical aid. Heatstroke can kill.
Heat exhaustion: Losing fluid and salt through perspiration or replacing them in an imbalanced way can lead to dizziness and weakness. Body temperature might rise, but not above 102 degrees. In some cases victims, especially the elderly, should be hospitalized. Heat exhaustion is more likely after a few days of a heat wave than when one is just beginning. The best defense is to take it easy and drink plenty of water. Don't take salt tablets without consulting a physician.
Heat syncope or fainting: Anyone not used to exercising in the heat can experience a quick drop in blood pressure that can lead to fainting. As with heat cramps, the cure is to take it easy.