A heat wave is an extended period of unusually high temperatures and often high humidity that causes temporary modifications in lifestyle and may have adverse health effects on the affected population. The World Meteorological Organization (WMO) defines a heat wave as a period during which the daily maximum temperature exceeds for more than five consecutive days the maximum normal temper- ature by 9 degrees Fahrenheit (5 degrees Celsius), the normal period being defined as 1961–1990