Multi‐Country‐Multi‐City Characterisation of Heat Stress and Exposure in Africa

Abstract

ABSTRACT This study presents the first continent‐wide assessment of long‐term (1974–2023) summer heat stress in Africa using the Universal Thermal Climate Index (UTCI) derived from ERA5‐HEAT reanalysis datasets. Employing a grid‐specific definition of summer, we analysed UTCI trends across spatial (continental to city scale) and temporal (decadal to hourly) dimensions. While annual UTCI anomalies range 0.2°C–1.6°C, substantial intensification emerges at finer scales. The frequency, duration and spatial extent of ‘very strong’ (38°C–46°C) and ‘extreme’ (≥ 46°C) heat stress have increased markedly, particularly, in the Sahel. Heat‐stressed hours (UTCI > 32°C) rose by 2%–25% across most countries, with extreme events doubling in 3–5 and 6–8 days episodes. City‐level analyses reveal escalating risks in large urban centres like Cairo, Lagos and Kano. As climate projections indicate further intensification, the findings underscore the urgent need for targeted heat‐health adaptation and early warning systems to protect vulnerable populations across the continent.