Heat stress symptoms are prevalent among people in buildings that are poorly ventilated or insulated, or constructed with unsuitable materials . These features are common to many structures in Africa, including slums, informal and low-income settlements, as well as schools and healthcare facilities . Temperatures inside these structures can exceed outdoor temperatures by 4ºC or more and have large diurnal fluctuations . Daily wage labourers and residents of urban informal settlements are among the most vulnerable to heat stress because of the urban heat island effect, with congestion, and inadequate ventilation, shade, open space and vegetation  being associated with impacts of both hot and cold conditions on public health . Temperature extremes are expected to result in relatively more deaths in informal settlements than in other settlement types .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report