Potential impacts of climate change on heat stress risks and country ranking across Africa

Heat stress poses a growing threat to human health and socio-economic development across Africa. While previous studies have examined how climate change may intensify hazards and exposure, less attention has been given to how these changes could reshape relative risk levels between countries, an important consideration for adaptation planning. This study assesses and projects heat stress risk across Africa using 12 multi-model simulations from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP-CMIP6). Daily heat stress was quantified using the Heat Index (HI), which combines air temperature and relative humidity. Risk was defined as a function of hazard, exposure, and vulnerability. African countries were ranked under present-day climate conditions and three future scenarios (SSP1–2.6, SSP2–4.5, SSP5–8.5). Maximum annual HI values currently occur in the tropics and increase under all future scenarios. Safe heat stress conditions decline sharply, shrinking from approximately 65% of Africa's land area today to about 20% under SSP5–8.5, with West Africa losing all Safe zones. South Sudan is a present-day hotspot of heat stress hazard, although future rankings shift, with Ghana overtaking South Sudan. Exposure rankings consistently place Nigeria first, while the Democratic Republic of the Congo rises to second. Heat stress risk increases by 40–60% under SSP5–8.5, with substantial redistribution across regions. Risk rankings confirm persistent hotspots in Nigeria, Ghana, Sudan and the Democratic Republic of the Congo, while identifying Uganda, Tanzania, and Chad as emerging areas of concern. Comparisons of additive and multiplicative approaches reveal sensitivity to methodological choices and associated uncertainties. These findings underscore the need for targeted adaptation measures, although these rankings should be interpreted as qualitative indicators rather than precise quantitative estimates. Practical Implications Climate change is intensifying heat stress across Africa, posing serious risks to public health, urban infrastructure, and socioeconomic development. This study provides a continent-wide assessment of current and future heat stress hazards using high-resolution climate projections and the U.S. National Weather Service heat index algorithm. By ranking African countries under multiple climate scenarios, the findings offer actionable insights for diverse stakeholders—health officials, urban planners, and international donors—who play critical roles in building resilience and protecting vulnerable populations. Health Officials The projected rise in heat stress across Africa presents a growing public health challenge that demands immediate attention. With increasing frequency and intensity of heat-related hazards—especially in countries like Nigeria, Ghana, and South Sudan—health systems must prepare for a surge in heat-induced illnesses. The expansion of Caution, Ex-Caution, and Danger zones underscores the need for robust early warning systems, heat-health action plans, and public awareness campaigns. Health ministries should integrate climate projections into national health strategies, prioritize vulnerable populations, and invest in training healthcare workers to recognize and manage heat-related conditions. These findings offer a data-driven foundation for proactive, life-saving interventions. Urban Planners This study highlights the critical need for climate-resilient urban design in Africa's rapidly growing cities. As heat stress hazards intensify—particularly in low-lying coastal and tropical regions—urban planners must incorporate heat mitigation strategies such as green infrastructure, reflective materials, and improved ventilation in building codes. The spatially detailed projections provide actionable insights for identifying high-risk zones and prioritizing interventions. Cities like Lagos, Accra, and Juba will require targeted adaptation to protect residents, especially in informal settlements. Planning for shaded public spaces, heat-resilient transport systems, and emergency cooling centers will be essential to safeguard urban populations in a warming climate. International Donors and Development Agencies The escalating heat stress risk across Africa calls for urgent, targeted investment in climate adaptation. This study identifies not only current hotspots like Nigeria and South Sudan but also emerging risk zones under future climate scenarios. Development partners should prioritize funding for heat-resilient infrastructure, early warning systems, and public health preparedness, particularly in countries projected to rise in risk rankings. The data-driven approach offers a valuable tool for guiding resource allocation and monitoring adaptation progress. Supporting national and local climate services to integrate these projections will enhance resilience and equity in climate response across the continent.