Heatwaves are prolonged periods of unusually hot weather, which may or may not be accompanied by high humidity. The World Meteorological Organization definition of a heatwave is ‘when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 °C. The perception of a heatwave varies geographically because it is measured relative to the average temperature in that area. For example, weather that is experienced as normal heat in summertime in Gambela town would be considered a heatwave in Addis Ababa city, where the average summer temperature is much cooler.
Heatwaves are a big challenge in low-income countries like Ethiopia, because energy resources for cooling and air conditioning are often lacking. Heatwaves can cause adverse health effects and even death when severe dehydration of the body results from excessive sweating. It is very important to drink plenty of water during a heatwave to replace lost fluids. When heatwaves occur in areas of Ethiopia with water shortages, people cannot get enough water to drink or to cool themselves, so provision of an adequate and safe water supply is important to reduce the impacts on human health.