Very hot and humid weather often leads to numerous health issues, ranging from heat cramps to death. Due to changing climatic conditions and to demographic growth, the number of people exposed to very hot and humid days is increasing worldwide. This is particularly the case across the African continent, where population growth is rapidly increasing and very hot and humid days are becoming more and more frequent, particularly in tropical areas. In this study, we consider more than 150 large African cities across 43 countries and project the number of people that will be exposed to dangerous heat conditions. Our projections suggest that this number will be 20 to 52 times higher at the end of the 21st century than currently. Large cities in Western and Central Africa appear to be particularly at risk, whereas cities in Southern Africa will remain relatively unscathed. We also show that a restrained urban demographic growth could lead to a 50% reduction in the number of people exposed to dangerous heat conditions. Population and urbanization policies should be part of the wide range of urban climate adaptation options in order to minimize future exposure to extreme heat.