Surface temperature from Landsat 9 Collection 2 Level 2 (ST_B10), converted to °C. Heatwave scenes selected per city — most from summer 2024; UK cities from May 2026. Hex grid: building-level mean LST aggregated to ~200m hexagonal cells. Berlin: partial Landsat scene coverage (southern portion only). Unpublished analysis by Dr Thami Croeser, June 2026.