From Heat Hazard to Dynamic Exposure: A Human-Centered Assessment of Urban Heat Burden for Evaluating Adaptation Limits

Urban heat risk is commonly assessed through physical hazard indicators and static heat hotspot maps, which are effective for identifying “hot spots” but provide limited insight into who is exposed to heat, when and where exposure occurs, and how long exposure persists. In reality, heat-related impacts are shaped by the cumulative thermal burden experienced through daily routines, occupational heat exposure, and mobility constraints. Moving beyond identifying where it is hot, efficient and equitable urban heat adaptation therefore requires quantifying the population-level heat burden experienced by residents and identifying strategies that can meaningfully reduce it. However, the lack of metrics to quantify residual heat exposure constrains local governments’ ability to assess adaptation effectiveness and identify adaptation limits. To address this gap and to enable the measurement of human-centered, quantifiable heat burden, we propose a conceptual shift from heat hazard to dynamic exposure, defined as population-level cumulative exposure differentiated by activity patterns and spatial locations across occupational, gender, and age groups, thereby explicitly incorporating vulnerability and behavioral dimensions of heat burden. By combining temperature distributions derived from a microclimate model with resident group activity patterns generated through behavioral analysis, we model city-level dynamic heat exposure and express it as time above a heat threshold to enable linkage with heat-related health impacts. The approach is applied to a case study of Suwon, South Korea. Modelled cumulative heat exposure is validated using Living Lab outcomes, specifically real-world exposure data collected from residents using portable temperature sensors. Future levels of dynamic heat exposure are evaluated under alternative future climate and socio-economic conditions. The effectiveness of heat adaptation portfolios, including technical, institutional, and behavioral options, is assessed in terms of their potential to reduce population-level heat exposure, drawing on evidence from the literature. We further conduct an illustrative analysis to examine how adaptation portfolios can reduce regional heat burden and to estimate the magnitude of residual exposure that may persist under future conditions. The results show that the proposed dynamic heat exposure model aligns closely with real-world observations, reproducing comparable patterns of cumulative heat exposure across population groups. Our result indicates that workers experience approximately 60% longer heat exposure durations than other groups. In addition, individuals in their 50s are exposed both for longer periods and at higher temperatures. The findings further suggest that conventional outdoor weather-station-based approaches may underestimate human heat exposure by approximately 30%. By quantifying urban heat burden as population-level dynamic heat exposure, this study moves beyond static hazard indicators to capture when, where, and to whom heat risk is actually experienced. This human-centered metric enables the evaluation of adaptation policy portfolios and move forward to ambitious goals. From a policy perspective, the approach supports needs-based local adaptation planning by aligning interventions with spatiotemporal exposure patterns and population groups facing the greatest constraints.