<p>As global climate change intensifies, the urban heat island (UHI) has become an increasingly significant challenge, impacting both urban environments and public health. We used the SSP-RCP model to analyze the spatiotemporal dynamics of heat and cold island patches in Fuzhou under projected climate change, integrating spatial analysis and network evolution theory. The results show that: (1) Cold island patches are generally decreasing in size, while heat island patches are expanding. The most significant increase in heat island area occurs under the SSP585 scenario; (2) The spatial distribution of heat and cold sources has shifted, with cold sources moving from southwest to northeast and heat sources from south to north; (3) Climate change scenarios exert a substantial influence on the urban thermal environment (UTE). In low-intensity scenarios, the reduction of cold islands and the expansion of heat islands may exacerbate the heat island effect. Conversely, in high-intensity scenarios, the intensification of the heat network may further aggravate the UTE; (4) Synergistic development of cities within metropolitan areas, strengthening the connectivity of cold networks, and enhancing the resilience of heat networks are crucial strategies for mitigating the negative impacts of UHI and improving cities’ capacity to cope with climate change. This study reveals the spatial and temporal evolution of heat and cold networks in the Fuzhou metropolitan area, providing a theoretical foundation for UHI mitigation under varying development scenarios and for the optimization and adaptation of UTE in response to future climate change.</p>