On May 30, it is informed from the National Climate Centre (NCC) of China Meteorological Administration (CMA) that the 2025 South China Sea summer monsoon broke out in the last pentad of May, which was later than the average outbreak time. The outbreak of the South China Sea summer monsoon marks the beginning of the East Asian summer monsoon. After the summer monsoon breaks out, the monsoon rain belt will gradually move northward from the South China region, and China will gradually enter the main flood season.

The South China Sea summer monsoon is an important component of the Asian monsoon system. Its prevalence is closely correlated to the summer precipitation in East Asia. Under normal circumstances, within two weeks after the monsoon outbreak, the monsoon air current will carry abundant southwest warm and humid water vapor from the tropical Indian Ocean and the South China Sea to the East Asian continent. The convective heavy precipitation process in the area south of the Yangtze River will conspicuously increase and intensify.

The outbreak of the South China Sea summer monsoon is one of the major turning points in climate and season in the Asian region. Since then, monsoon air currents and precipitation have gradually advanced northward, northeast and northwest. The rainy season in South China will continue, and the rainy season in Southwest China and the plum rain season in the Yangtze River Basin will also unfold one after another. The heat and moisture balance in Asia will be disrupted. Special precautions should be taken against urban flooding, floods in small and medium-sized rivers, mountain torrents and geological disasters caused by the continuous excessive precipitation.

Editor: LIU Shuqiao