Arctic warming delays the Afro-Asian monsoon retreat amplifying autumn rainfall

Abstract The Afro-Asian summer monsoon (AfroA-SM) provides essential rainfall for billions of people. However, in recent decades, unusually wet conditions have persisted into autumn, creating unprecedented extremes. Using multidecadal observations, reanalysis datasets, and Polar Amplification Model Intercomparison Project (PAMIP) simulations, we show that Arctic warming significantly postpones the retreat of the AfroA-SM. This delay shifts the northernmost summer monsoon boundary by 5.6°–12° and accounts for 33%–69% of September precipitation across North Africa, South Asia, the Tibetan Plateau, and East Asia. The mechanism is anchored in a northward displacement of the subtropical jet stream, which is driven by reduced meridional temperature gradients resulting from sea‐ice loss and Arctic amplification. The resulting Eurasian anticyclone weakens the tropospheric dipole of the polar vortex, promoting negative North Atlantic Oscillation (NAO)-like anomalies and a pronounced Eurasian wave train. These reinforce the northward shift of the subtropical high and enhance warm‐moisture advection into northernmost margin summer monsoon belts. PAMIP ensemble experiments further indicate that future Arctic amplification will intensify this autumn monsoon persistence and its associated precipitation. Our findings are critical for understanding the intensification of late-season hydroclimatic extremes, underscoring the urgent need for improved seasonal forecasting, adaptive agricultural strategies, and flood-risk management in a warming climate.