Urban expansion in polycentric postindustrial regions alters land cover and surface thermal patterns. This study assessed how these processes evolved in the Upper Silesian–Dąbrowa Basin Metropolis (Górnośląsko-Zagłębiowska Metropolia, hereafter GZM), Poland, between 1986 and 2023, using multi-temporal Landsat data. UAV thermal imagery was used only to support the local interpretation of selected thermal contrasts. The LULC classification distinguished four broad classes: agricultural land, anthropogenic surfaces, forest areas, and water bodies. Over the study period, anthropogenic surfaces increased overall, whereas agricultural land declined. Forest areas remained an important part of the metropolitan landscape, although their spatial pattern became more fragmented and its total share decreased by the end of the study period. The transition matrix showed that the main land cover conversion was from agricultural land to anthropogenic surfaces, indicating that urban growth occurred mainly at the expense of open/ non-forest vegetated land. LST patterns were closely related to land cover. The highest temperatures occurred in built up, industrial, and transport areas, whereas lower values were associated with forest and water surfaces. Areas of elevated summer LST became more continuous within the metropolitan core, especially along major transport corridors. UAV imagery revealed pronounced local thermal contrasts within warm Landsat pixels, but it was treated as qualitative support rather than direct validation of satellite derived temperatures. Overall, the results show that long term land cover change played a major role in shaping the thermal structure of the GZM and provide spatially explicit information relevant to planning and climate adaptation.