Heat kills by taxing the human body beyond its abilities. In a normal year, about 175 Americans succomb to the demands of summer heat. Among the large continental family of natural hazards, only the cold of winter--not lightning, hurricanes, tornadoes, floods, or earthquakes-- takes a greater toll. In the 40-year period from 1936 through 1975, nearly 20,000 people were killed in the United States by the effects of heat and solar radiation. In the disastrous heat wave of 1980, more then 1,250 people died.

And these are the direct casualties. No one can know how many more deaths are advanced by heatwave weather--how many diseased or aging hearts surrender that under better conditions would have continued functioning.

North American summers are hot; most summers see heat waves in one section or another of the United States. East of the Rockies, they tend to combine both high temperature and high humidities, although some of the worst have been catastrophically dry.