Heat Wave

Aheat wave is a prolonged period of unusually warm and humid weather, lasting for a period of days to weeks; a minimum of three consecutive hot days is a common rule of thumb. Similarly, the temperature threshold that indicates a heat wave depends on what is normal for the region. In assessing [Page 859]the impact of a heat wave, the most useful measure is the apparent temperature, which is an index that combines air temperature and humidity to assess the total stress that individuals will experience.

Heat waves create uncomfortable conditions, and are often associated with increases in human mortality. The hot, humid conditions characteristic of heat waves raise the body temperature while simultaneously limiting evaporative cooling, producing discomfort and increased stress on the body. Heat ...