In　light　of　escalating　urbanization　and　climate　change,　understanding　the　Urban　Heat　Island　(UHI)　effect　is　crucial　to　improving　urban　resilience.　The　Local　Climate　Zones　(LCZs)　classification,　introduced　in　2012,　has　become　a　vital　tool　in　urban　climate　research.　While　most　studies　focus　on　inter-LCZ　heterogeneity　(temperature　differences　between　LCZ　types),　this　study　highlights　the　less-explored　intra-LCZ　heterogeneity　(variations　within　the　same　LCZ　type).　Using　ECOSTRESS　LST　data,　we　examine　spatial　and　diurnal　LST　variations　in　Fuzhou,　China—a　representative　＇Furnace　City＇.　Random　Forest　models　and　Shapley　values　analysis　reveal　that　external　factors,　such　as　distance　to　the　city　center　and　proximity　to　hotspots　(like　LCZ　3　or　8)　or　blue–green　infrastructure,　play　significant　roles　in　both　inter-　and　intra-LCZ　LST　variability.　Water　bodies　typically　lower　surrounding　daytime　temperatures　but　increase　them　at　night,　while　greenery　consistently　mitigates　surrounding　LST　throughout　the　day.　Our　findings　suggest　that　applying　the　LCZ　framework　requires　not　only　attention　to　local　(　100　m)　surface　properties　but　also　consideration　of　neighborhood　and　city-scale　characteristics　to　better　capture　the　spatio-temporal　heterogeneity　of　urban　thermal　environments.　These　insights　emphasize　the　need　for　urban　planning　strategies　that　integrate　blue–green　infrastructure　and　manage　thermal　hotspots　to　mitigate　UHI　effects.　©　2025　Elsevier　Ltd