As urbanization accelerates, the thermal environment of urban areas has become a critical aspect of city planning. However, a mismatch between cooling supply and demand persists, and its underlying factors are not fully understood. This study calculates the supply–demand index for urban blue and green spaces and utilizes the LISA model to pinpoint areas with imbalanced cooling supply and demand. Key findings include: 1) Surface temperatures in Hangzhou’s main urban area rose from 2016 to 2022, exacerbating thermal issues; 2) The supply–demand indices of blue and green spaces show spatial variation; 3) Areas with low supply and high demand are closely linked to socio-economic and built environments, while those with high supply and low demand are more influenced by natural factors. These results offer insights for improving urban heat and cooling strategies.