Abstract:In the summer (June to August) of 2018, precipitation was more than average over North China and South China, while it was less over the middle part of East China. Especially, floods were severe in the Yellow River Basin and droughts were observed in the Yangtze River Valley. The pre flood season in South China and Meiyu season began later relatively, while the rainy season in North China began earlier. All these features were well predicted in the climate operation. The forecast also captured the anomalous features of the tropical cyclone frequency, tracks, intensity and active/inactive periods over the Northwest Pacific and South China Sea in 2018. Moreover, the forecast provided a correct prediction of the surface air temperature which was higher than average in most regions of China. Both diagnostic analyses and results from dynamic models were used to make the summer climate prediction in 2018. For the diagnostic analyses, La Ni〖AKn~D〗a event and the cold tropical Indian Ocean were considered to be important predictors. Under the influence of the tropical SSTA, the western Pacific subtropical high (WPSH) tended to stay more northward, cyclonic circulation anomaly dominated the Philippines and the East Asian summer monsoon (EASM) was stronger than normal. Dynamic climate models from Beijing Climate Centre and abroad showed similar results of the prediction for the key members of EASM system. The results of diagnostic analyses and dynamic models all indicated that the La Ni〖AKn~D〗a event and the cold tropical Indian Ocean were important precursory signals for the prediction of the climate anomaly in summer 2018, which supported less rainfall in the middle and lower reaches of the Yangtze River and more in northern part of China.