The East Asian summer monsoon (EASM) stands as the most northerly extending monsoon system, defined by its remarkable seasonal march. It features a stepwise northward migration of rainfall stages, starting with the pre-Meiyu season in southern China in mid-May, progressing into the Meiyu season (known as Baiu in Japan and Changma in Korea) from mid-June to mid-July, and ultimately extending to northern China by mid-July.