Continuing climate change has led to an increase in worldwide temperatures and more frequent weather extremes such as heatwaves. The heat-absorbing qualities of built-up urban areas makes them especially vulnerable to these high temperatures. This effect can have several negative impacts on public health and the quality of life in urban areas. Heat stress risk is currently increasing and expected to further increase due to three assumed root causes—urbanization, global warming and population aging. Urbanization leads to higher proportions of people exposed to, and intensification of, the heat island effect.