Heat islands in cities

The temperature in cities is usually higher than in the surrounding rural areas, giving rise to increased human exposure to heat stress during heat waves. The elderly and children are particularly affected by health problems. This indicator quantifies that increased exposure on the basis of the additional ‘heat-wave days’ measured in cities, which account for both the weight and the duration of heat waves. In this indicator, we take over the definition used by the Federal Public Service for a heat wave: “a period of at least three consecutive days with an average minimum temperature (average over the three days and not per day) exceeding 18.2 °C and an average maximum temperature exceeding 29.6 °C”.