Abstract:During the summer of 2017 (June to August), the average precipitation over China was 348.6 mm, which is 8.1% more than the climate mean (332.6 mm). Two rainfall belts were observed over eastern China. The average temperature in summer was 21.7℃, which is 0.8℃ higher than the climate mean (20.9℃). The summer of 2017 is the second warmest since 1961. The East Asian summer monsoon (EASM) was weaker than normal, while the West Pacific subtropical high (WPSH) was significantly stronger than normal with southward ridge position. The anomalous Philippine Sea anticyclone controlled the lower troposphere. The “-+-” circulation pattern was located in Eurasian mid high latitude, with negative anomalous over Ural Mountain and near Japan and positive anomalous over Baikal Region. Circulation configuration of low latitudes and mid high latitudes resulted in anomalous convergence of moisture flux and more precipitation over the south of the Yangtze River. Further analysis indicated that the interdecadal strengthening of West Pacific subtropical high and the sea surface temperature anomalies over the central and eastern tropical Pacific changing from negative to positive are the important cause for the significantly more precipitation over the south of the Yangtze River.