Hourly precipitation data during the warm season (May to September) of 2011–2021 in Chongqing were used to analyze the diurnal variation characteristics. Results reveal a pronounced “night rain” phenomenon, with primary peaks from midnight to early morning and secondary peaks in late afternoon. These peaks and early-night troughs are generally consistent across annual and monthly changes, oscillating every 2–3 years, alternating between trough and peak years. Peak periods are May to June and September, while July to August are trough periods. Precipitation amount (PA), frequency (PF), and intensity (PI) peak phase generally delayed from west to east and south to north. Mountainous topography tends to moderate fluctuations in diurnal precipitation. Central and western regions mainly affected by synoptic systems, PA is mainly contributed by PF, and eastern regions influenced by terrain, PA is mainly contributed by PI. East-west propagation of precipitation is more prominent than north-south, with abnormally high in western, south of northeastern and Daba mountain area. Short-duration precipitation events occur approximately twice as frequently as persistent ones, yet persistent precipitation events dominate warm-season rainfall contributions, accounting for over 80% in most regions. Early-morning persistent rainfall prevails in western Chongqing, while afternoon short-duration precipitation events dominate both south of northeastern Chongqing and the Daba Mountains, corresponding precisely to the primary and secondary peaks of the diurnal variation curve. All persistent events exhibit strong asymmetry: the time from onset to peak rainfall is significantly shorter than the duration from peak to cessation. Mountainous terrain delays the peak timing of persistent rainfall, prolonging the pre-peak phase.