Urban heat island (UHI) effect significantly influences the urban sustainability and health of cities and varies seasonally. However, spring and autumn have received less attention. Furthermore, research on long-term seasonal UHI changes and impacts is insufficient. This study examines the seasonal spatiotemporal dynamics and gradient characteristics of UHI in spring, summer, autumn, and winter in Changsha, a typical subtropical "furnace city" from 2006 to 2022. (1) Spatiotemporal dynamics: The high-temperature UHI (relatively high-temperature zone and high-temperature zone) range expands most...