Seven Landsat images were used to assess urban expansion and the corresponding thermal characteristics in Fuzhou City, China between 1985 and 2015. The urban surface thermal patterns were investigated by retrieving land surface temperature using a single-window algorithm based on atmospheric calibration. The built-up area doubled from 1985 (10.6 %) to 2015 (23.4 %), mostly from cropland conversions in the urban fringe, and was closely associated with population increase (R2?=?0.93), gross domestic production GDP (R2?=?0.97), and fixed asset investments (R2?=?0.9139), illustrating the contributions of socioeconomic factors to rapid urban expansion. The daytime heating effect (heat source) in urban areas was strongly related to urban expansion, with a high percentage of an impervious surface usually associated with a high surface temperature. The average range over which wetlands affected built-up area, farmland, and road was 381, 321, and 347?m, respectively. The area of influence on construction land and road was 151 and 11 km2, respectively, whereas the average value for farmland was 147?km2. The area of wetland influence decreased during the study period, and therefore one explanation for the increase in the urban heat island (UHI) in Fuzhou City was the weakened cooling effect of wetland.