East Asian summer floods and droughts exhibit a typical dipole pattern centered near 30°N, known as the southern drought–northern flood (SDNF) pattern. This pattern has caused significant economic losses and casualties in the past three decades. The Quasi-Biennial Oscillation (QBO), a tropical wind pattern above 10 km, is identified as a key predictor of this dipole pattern, contributing the largest explained variation. A statistical model incorporating the QBO can predict summer floods and droughts at least three months in advance and explain at least 75.8% of precipitation variation. The QBO's influence on the stratosphere is crucial, modulating zonal wind patterns and leading to meridional circulation anomalies that drive precipitation changes. The study highlights the importance of the QBO in understanding and predicting East Asian summer precipitation (EASP), providing a potential tool for seasonal forecasting.East Asian summer floods and droughts exhibit a typical dipole pattern centered near 30°N, known as the southern drought–northern flood (SDNF) pattern. This pattern has caused significant economic losses and casualties in the past three decades. The Quasi-Biennial Oscillation (QBO), a tropical wind pattern above 10 km, is identified as a key predictor of this dipole pattern, contributing the largest explained variation. A statistical model incorporating the QBO can predict summer floods and droughts at least three months in advance and explain at least 75.8% of precipitation variation. The QBO's influence on the stratosphere is crucial, modulating zonal wind patterns and leading to meridional circulation anomalies that drive precipitation changes. The study highlights the importance of the QBO in understanding and predicting East Asian summer precipitation (EASP), providing a potential tool for seasonal forecasting.