There is scant research on the association between humidex exposure and urinary system diseases. Hospitalization records from Lanzhou city were collected for the period 2015 to 2019, alongside daily meteorological and air pollution data for the study duration. Daily humidex was calculated using temperature and relative humidity indices. The study employed a combined approach of generalized additive models and distributed lag non-linear models (DLNMs) to estimate the exposure-lag-response relationship between humidex and hospital admissions for urinary system diseases, as well as for subgroups of diseases (urolithiasis and tubule-interstitial diseases). A total of 55,365 patients with urinary system diseases were included. The single lag effect of overall urinary system diseases was most significant on lag13 with the relative risk (RR) = 1.066 (95% confidence interval [CI]: 1.011, 1.124), while the cumulative lag effect over lag0-14 was most significant with RR = 1.387 (95% CI: 1.240, 1.550). The goal of this study was to establish an early warning system and allocate medical resources effectively to reduce hospital admissions for urinary system diseases.