ABSTRACT While thermal stress risks are global, Sahelian Africa's localised impacts remain understudied despite rapidly intensifying heat exposure. Climate hazards associated with human thermal stress present considerable challenges to Nigeria's public health and socio‐economic activities, with effects intensified by the nation's heterogeneous climatic characteristics. This research examines the spatial and temporal variability of heat stress in Nigeria from 1950 to 2023. WBGT was selected as the core indicator due to its strong relevance in humid climates and its ability to incorporate metabolic and radiative heat load. Hourly wet‐bulb globe temperature (WBGT) data were derived from 0.1° × 0.1° ERA5‐Land hourly reanalysis datasets using the Liljegren method and subsequently analysed for significant trends using the Mann–Kendall trend test. The results showed that Nigeria's annual mean of daily peak WBGT varies from 24°C in the south to above 28°C in the north. Over the 74‐year period, WBGT increased by approximately 1.2°C in northern Nigeria and by about 0.8°C–1.0°C in the southern regions, with northern regions showing the strongest trends (~0.20°C/decade). The late period (1987–2023) consistently exhibited higher WBGT values than the early period (1950–1986), with increases most pronounced during early morning and late evening hours. Late‐period WBGT values increased across all zones by 0.8°C–1.2°C from September to November, with the largest shifts in southern Nigeria during March–May. These rising WBGT levels have direct implications for public health, outdoor labour productivity and climate adaptation planning—potentially reducing agricultural and construction sector labour capacity by 10%–15% during peak heat months under current thresholds. The day and nighttime variability of WBGT decreased from north to south. These findings underscore urgent needs for improved urban planning (e.g., heat‐resilient infrastructure, shading, ventilation) and stronger rural health access systems to manage growing heat‐related risks. Overall, the study highlights escalating nationwide heat stress and calls for targeted adaptation strategies, including early‐warning systems, expansion of cooling access, occupational heat‐safety guidelines and heat‐sensitive urban and agricultural planning.
Nasara et al. (Sun,) studied this question.