Based on hourly rainfall data from 19 representative stations in Nanxi District, Yibin City, and ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) from 2009 to 2023, the climatic characteristics and influencing factors of short-term heavy rainfall in Nanxi District were analyzed. The results show that the annual frequency of short-term heavy rainfall in Nanxi District shows a significant increasing trend overall. Most events occur in the afternoon, evening and early morning (14:00—02:00), with regional heavy rainfall centers located in the southeastern and northwestern parts of the district. During short-term heavy rainfall events, the atmospheric stratification is highly unstable (K-index≥36°C) with ample low-level humidity (mean specific humidity at 850 hPa is 16.7 g/kg, and relative humidity is 84.4%). The frequency of short-term heavy rainfall with intensities ≥ 20 mm/h accounts for 54%, significantly higher than other intensity levels. The main weather systems responsible for short-duration heavy rainfall in this area include vortex shear systems, inverted troughs in the Sichuan Basin and easterly waves, the Western Pacific Subtropical High, and westerly troughs.