Comfort has not been the only thing destroyed by this summer's steam-bath weather. Some lives have been snuffed out too. Cook County Chief Medical Examiner Robert Stein counts 39 heat-related deaths so far in Chicago and its environs. Missouri has registered 30 deaths and 572 cases of heat-related illness. (The term encompasses both heatstroke and other conditions, like heart trouble, that are aggravated by the hot weather.) Many of the victims are old, poor or both. But not all: two men in their 20s died competing in New York City footraces.
Authorities suspect many heat deaths go unreported as such; they...