Exploring the variation trends of urban heat island (UHI) effects is critically important for sustainable urban development.UHI characteristics of Sanhe City, Hebei Province were investigated, using Landsat 8 satellite imagery. Land surface temperature (LST) was retrieved via the single-window algorithm, and visual interpretation and overlay analysis were employed to examine the relationship between urban green spaces and LST. The results show that from 2014 to 2020, the UHI effect in Sanhe undergoes significant changes, with high-temperature zones mainly distributed in residential and university areas. The normalized difference vegetation index (NDVI) is found to be negatively correlated with LST, and stronger cooling effects are observed in areas with higher NDVI values. Although green space area also shows a negative correlation with LST, the relationship is non-linear. The correlation between green space perimeter and LST is weak and becomes noticeable only when the number of samples is sufficiently large. Overall, green spaces have a cooling effect on surrounding areas; however, the extent of this effect is influenced by multiple factors. There is only a weak correlation between green space area and cooling range, indicating that simply increasing green space area does not directly expand the extent of temperature reduction. These findings provide scientific insights for urban green space planning and heat environment mitigation.