In the summer of 2023, China experienced a climate of higher temperature and less precipitation. Both the droughts and the floods showed remarkable spatial differences. Although the numbers of typhoons generated and landing in summer were both less than normal, the typhoons that formed were extremely destructive. In terms of temperature, persistent heat waves were the most prominent in North China and Northwest China since 1961, but the intensities of high temperature and drought were significantly weaker than those in the summer of 2022 across the Yangtze River Basin. The prediction effect has shown that the climate prediction successfully forecasted the characteristics of the rain belt in northern China, and made accurate prediction and early warning of the possible heavy floods in Songhua River Basin, Nenjiang River Basin and Haihe River Basin. The forecasted number, main track and affected area of tropical cyclones in summer were also consistent with the observation. Prediction skills of mean temperatures in most parts of China are higher than normal, especially the heat wave intensity in the Yangtze River Basin in 2023. The primary error of precipitation forecast in the rainy season mainly occurred in South China, and the extreme high temperature processes were underestimated for North China and Huanghuai Region. In addition, the precursors and their forecasting performance in summer 2023 are also reviewed and diagnosed. The results indicate that both the interdecadal and interannual variations of external forcing had good indicative significances for the prediction of rain belt in northern China. However, almost all the precursors gave consistent wrong information about the precipitation in South China, which was the main reason for the failure of precipitation forecast in South China.