In the autumn of 2023, Chongqing recorded its fourth highest precipitation total for the same period since 1961, and the highest during the monitoring period of the West China Autumn Rain (hereafter referred to as “autumn rain”). Using observational data from meteorological stations and ERA5 reanalysis data, the main reasons for the abnormal precipitation in autumn were analyzed. The results indicate that during both the autumn and autumn rain periods, the 500 hPa circulation pattern was characterized by a blocking high over Lake Baikal and mid-latitude low-pressure wave systems. Consequently, the Chongqing area was under a pattern of a ridge to the north and a trough to the south, with frequent influences from short-wave troughs and other low-value systems in the westerlies. At the same time, the western Pacific subtropical high (WPSH) was persistently more intense, extensive, and displaced further westward and northward than usual, continuously transporting abundant moisture to the Chongqing region through its periphery. The combination of the anomalously strong warm, moist airflow and frequent low-value systems such as westerly short-wave troughs led to exceptionally abundant moisture and prolonged convergence over Chongqing, resulting in frequent rainstorms and abnormal precipitation. The autumn precipitation in Chongqing showed limited sensitivity to the ENSO warm event starting in early summer, with its increased climate variability playing a more dominant role than the influence of the ENSO warm event. Furthermore, the continuously warm sea surface temperatures of the Indian Ocean may have served as an important external forcing factor, which indirectly led to the abnormal increase of autumn precipitation in Chongqing by affecting the WPSH.