Extreme heat has increasingly threatened urban health and well-being, making the assessment of heat vulnerability a growing research priority. Existing heat vulnerability studies mainly focus on coarse administrative or census-level scales and define adaptive capacity as distance-based accessibility of cooling resources. As a result, fine-scale spatial heterogeneity in heat vulnerability and the thermal burden experienced during travel to inform heat adaptation strategies are often overlooked. Considering these limitations, this study proposed a novel heat vulnerability framework that incorporates heat exposure based on a modified temperature-humidity index (MTHI), grid-level sensitivity and mobility-based adaptive capacity in relation to accumulated heat stress. A case study of Wuhan showed distinct urban-rural differences, with urban vulnerability driven by high exposure and sensitivity, and rural vulnerability shaped by limited accessibility to cooling resources. This research emphasises the importance of incorporating fine-scaled measures of mobility and heat stress into heat vulnerability assessments to better support targeted planning and heat mitigation strategies.