The increase in the frequency and intensity of extreme heat events (EHEs), potentially associated with climate change in the near future, highlights the importance of heat health risks assessment, which is an important starting point for the reduction of heat-related mortality and sustainable development. However, there is a spatiotemporal mismatch between hazard data (at pixel-level) and exposure data (at census unit level) in heat health risks assessment. Based on multisensor remote sensing data and demographic and socioeconomic statistical data, we used a human settlement index to assess heat exposure. Heat health risks and its driving factors were spatially explicitly assessed and mapped at the 250 m *250 m pixel-level across the Yangtze River Delta region (YRD). The visual inspection suggests that the high risks areas were mainly distributed in urbanized areas of YRD, including the downtown of Shanghai, Changzhou, Hangzhou, Ningbo, Wuxi, Jiaxing and Taizhou, which was mostly driven by the high human exposure and heat hazard index. In less-urbanized cities and the suburban and rural areas of mega-cities, the heat health risks come second. Even though the human exposure index was low in other less-developed areas, the heat health risks in those areas were high due to the high heat hazard and human vulnerability index. It's of great importance to identify the driving factors of high heat health risks to provide science-based support for adaptation strategies and emergency planning.