Abstract:The general atmospheric circulation in September 2025 was characterized by the following key features: the Northern Hemisphere polar vortex exhibited a single core structure, and biased toward the Eastern Hemisphere. The western Pacific subtropical high (WPSH) was stronger than usual, with its ridge extending farther westward and northward. Under its persistent control, prolonged high temperature conditions occurred in southern China. The warm and humid airflow on the edge of the WPSH converged with cold air moving southward, leading to significantly increased autumn rain in West China. Most of northern China was influenced by relatively flat westerly flow, with limited incursions of cold air. The temperature in North China and Northeast China was relatively high and the precipitation was relatively low. A total of six tropical cyclones or typhoons formed in the month, three of which made landfall in China, and the both figures exceeded the climatological normal by 1 and 1.3, respectively. On 18 September, tyhpoons Mitag, Ragasa and Neoguri successively formed and coexisted. Mitag， Ragasa and Bualoi tracked northwestward, affecting South China, etc. Super Typhoon Ragasa made landfall three times along the southern coast, accompanied by strong winds and prolonged influence. Persistent moisture transport by the WPSH, combined with the effects of tropical cyclones, resulted in significant precipitation across South China. The monthly mean temperature across China was 18.1℃, 1.2℃ above normal, ranking as the fourth highest since 1961. The national average monthly precipitation reached 87.6 mm, 34% above the normal, making it the third in September since 1961. In addition, eight major heavy precipitation processes and four severe convective weather processes were recorded during this month.