Deadly Degrees: Why Heat Waves Kill So Quickly

An intense heat wave that sent temperatures in Phoenix to 118 degrees Fahrenheit (47.7 degrees Celsius) this weekend has killed four people — and the heat could be worse today. Those killed so far were all hiking or biking outdoors, but heat waves can kill close to home, too. In 2003, during a major European heat wave, 14,802 people died of hyperthermia in France alone.