Abstract: During summertime, the WPSH (western Pacific subtropical high) exhibits two northward jumps. The first jump signals the termination of pre-flood period in southern China and the start of the Meiyu over the Yangtze-Huaihe River valley; the second jump indicates the termination of the Meiyu and the start of rainy season in northern China. Based on the fast Fourier transformation and composite analysis of observational and reanalysis data, the authors investigated the impact of the intraseasonal oscillations (ISOs) on various time-scales on the northward jumps in the normal and abnormal years. The dominant periods of the ISOs are different in normal and abnormal years, i.e. 10-20 days and quasi-60 days in normal years, 30-60 days in abnormal years of the first jump and earlier years of the second jump, 10-20 days and 30-60 days in later years of the second jump. During the annual cycle, the ISOs tend to propagate northward in the East Asian-tropical northwestern Pacific region, leading to the northward jump of the WPSH. With the northeastward propagation of the ISOs over the Indian monsoon region, a more remarkable first jump is observed due to the eastward extension of the westerly. By contrast, the biweekly oscillation of the warm pool convection triggered by the cold air invasion from the Australian high plays an important role in a more evident second jump during the normal and later years. The sea surface temperature anomaly over the northwestern Indian Ocean in the preceding spring leads to the phase migration of local ISOs and associated abnormal first jump. Besides, the time-scale and amplitude of the ISOs in the warm pool can be regulated by ENSO, resulting in the abnormal second jump.