A remote sensing-based surface thermal stress index for assessing urban heat dynamics in Greater Cairo

Rapid urban growth has reshaped surface thermal conditions in Greater Cairo. This study applies a Surface Thermal Stress Index (STSI) integrating normalised land surface temperature (LST), NDVI, and NDBI from Landsat 8 annual composites processed in Google Earth Engine for 2015 and 2025. Higher STSI values indicate more favourable surface conditions rather than physiological thermal comfort. Using common spatial support, fixed pooled normalisation bounds, and weights of 0.35/0.30/0.35, mean LST decreased from 33.61 to 31.62 °C, while mean STSI increased from 0.44646 to 0.48248. The lowest score class, defined by a fixed 2015 quintile cutoff, contracted from 20.00% to 5.23% of the area. Alternative-weight maps remained strongly correlated with the baseline (r = 0.984–0.999), although priority-area boundaries varied. Year-matched population overlays, MODIS comparisons, and Landsat land-cover transitions provide demographic, thermal, and land-surface context. STSI offers a reproducible framework for preliminary daytime surface screening alongside component maps and sensitivity results.