Associations Between Grey–Green Morphology and Surface Urban Heat Island Intensity Across Five Climate Zones: A Multi-City Block–Local Climate Zone Perspective for Sustainable Urban Heat Mitigation

Global urbanization has reshaped grey–green spatial patterns and intensified surface urban heat islands, posing challenges for sustainable urban development. However, cross-regional multi-city studies of associations between grey–green morphology and surface UHII remain limited, while conventional urban–rural comparisons can obscure intra-urban thermal differentiation. This study applies a block–local climate zone (LCZ) framework to 150 Chinese cities across five climate zones. Clear-sky daytime Landsat 8 LST composites for June–September 2023 and multi-source spatial data were integrated at the block scale to quantify surface urban heat island intensity (UHII) and 18 2D and 3D grey–green morphological indicators. CatBoost–SHAP was used to examine predictor importance and nonlinear associations across climate zones. The mean surface UHII across the 150 cities was 1.65 °C; 138 cities showed positive values, with an overall south-high, north-low pattern. Intra-urban thermal differentiation was pronounced, with LCZ 8 exhibiting the highest surface UHII and LCZ A the lowest. At the climate-zone scale, DEM was the highest-ranked predictor in the middle temperate zone, whereas SPL_Grey ranked first in the southern temperate and three subtropical zones. At the city scale, the highest-ranked predictor shifted from DEM to SPL_Grey from north to south, while NDVI, FVC, and LAI showed recurring contributions across climate zones. SHAP dependence curves indicated model-derived response ranges, including NDVI values of 0.41–0.57 and building-density values of 10–25%. These findings provide comparative, block-scale evidence for climate-responsive grey–green spatial planning and sustainable urban heat mitigation.