Night-time urban heat exposure: Overheating and thermal resilience of South American bedrooms

The intersection of urban heat exposure and housing vulnerability remains poorly understood in the Global South. This study introduces one of the first empirical assessments of night-time overheating and thermal resilience in South American bedrooms during heat waves, while proposing a criterion that links overheating and a resilience score. We monitored 15 bedrooms in Salta, Argentina, over the 2023–2024 cooling season, which included seven heatwaves. Air temperatures ranged 18.8–31.7 ${}^{\circ }C$, with 39% of night-time values exceeding 26 ${}^{\circ }C$, temperatures that can compromise sleep quality and health. Overheating occurred on 33% of nights, and notably, it often peaked after heatwave ends due to buildings’ thermal inertia. Bedrooms on upper floors and in denser urban areas were more vulnerable, while ground-floor and air-conditioned spaces showed greater resilience. Importantly, prolonged heatwaves posed greater risks than shorter and more intense ones, and 65% of bedrooms experienced strong or extreme overheating. These findings highlight an urgent need to rethink housing design and urban policies in Latin America, where mechanical cooling is not universally accessible. By providing high-resolution thermal data from an understudied region, this study supports the development of equitable, passive cooling strategies and inclusive frameworks for assessing thermal risk under climate extremes.