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Very little research has documented the exposure of populations in Africa to extreme heat. We measured indoor air temperature and humidity hourly for 13 months in seven houses of contrasted architecture and construction materials all in the northern neighbourhoods of Ouagadougou, Burkina Faso. These measurements are compared to air temperatures recorded at the synoptic weather station of Ouagadougou airport and to land surface temperature estimates from Landsat satellite images at seven dates with clear-sky conditions. The results reveal huge temperature differences (exceeding 10 °C) between houses, especially in the afternoon hours of the warmest season. Indoor temperature is also much more variable than land surface (outdoor) temperature in the same locations, as estimated by satellite imagery. Houses with greater thermal inertia smooth the afternoon temperature peak, reducing heat exposure. Heat stress bioindicators reveal that danger thresholds, while rarely reached in some houses, are frequently exceeded in others year round except for the core of the cold winter season (December and January). In spring, the hottest season, the danger threshold is almost permanently exceeded in these dwellings, exposing their inhabitants to significant heat stress. This pilot study shows the primary role of housing in modulating indoor temperature, raising questions of public health and habitability of Sahelian regions in a warming world. This issue will be of increasing importance with ongoing climate change, hence the need for further, more detailed instrumented campaigns in African settlements. Highlights. 1. Indoor temperatures vary tremendously between houses. 2. Contrasts between houses are greatest in the hottest hours of the warm season. 3. Thermal danger or extreme danger levels are often exceeded in some houses. 4. In some houses, heat stress may occur in all seasons except winter. 5. More instrumented campaigns for heat stress in African housing are needed.

openalex: W3202114744