This project tackles the critical need for heat adaptation in cities. As intensifying heatwaves increasingly threaten lives and economic productivity, this study develops a novel measure to assess future tourism-related heat hazards, examines the added strain on city response systems by tourism, and establishes new insights into differentiated vulnerabilities amongst tourists and workers. By integrating a global analysis with three city case studies, this research co-develops innovative responses to reduce heat risk within urban systems. A new set of adaptation principles will help prioritize low-carbon, just responses, implemented through collaborative governance systems across different scales and sectors.