Urban discomfort under thermal–humidity stress poses escalating challenges in rapidly urbanizing and climatically sensitive regions. This study investigates the driving role of wet-bulb temperature (Tw) in shaping urban comfort dynamics across the Lanzhou–Xining urban agglomeration from 2000 to 2024. A multi-source framework is developed to derive high-resolution Tw using meteorological reanalysis data and to construct a temporal data cube of functional comfort indicators, encompassing thermal l