Patch size and vegetation condition influence surface-temperature contrasts around urban green patches in a humid subtropical city

Urban regions in the humid subtropics are undergoing rapid land conversion, vegetation loss and intensifying heat exposure. Yet patch-level evidence for urban green-space cooling remains limited. We analysed 456 urban and peri-urban green patches in Lucknow, India using Landsat 8 land surface temperature (LST), Sentinel-2 vegetation indicators, and patch metrics for summer and winter scenes in 2019 and 2024. Cooling was quantified as patch-to-matrix surface temperature contrast (ΔLST) relative to built-up surroundings. Green patches were generally cooler than adjacent built-up areas, with median warm-season ΔLST of about 0.6–0.8 °C and local maxima exceeding 2 °C. ΔLST increased from approximately 1 ha into the medium-size range and then showed diminishing gains beyond about 8–10 ha range. Buffer analyses indicated detectable surface-temperature contrasts over the first 100–200 m of surrounding built-up matrix, after which the curves generally flattened. Vegetation condition was more strongly associated with ΔLST in summer than in winter, while simple shape metrics explained little additional variation. Peri-urban patches showed stronger contrasts than urban patches, although this comparison remains partly confounded by matrix context. The study translates established park-cooling concepts into conservative, decision-oriented indicators for land-constrained humid subtropical cities. It emphasizes on the protection of canopy-rich patches, improvement of vegetation condition in smaller patches and reduction of impervious gaps between green spaces.