Extreme East Asian summer monsoon (EASM) rainfall frequently induces floods. While generally attributed to internal climate variability, this study presents evidence for significant EASM intensification following strong tropical volcanic eruptions. Multi-proxy analyses reveal increased EASM in the first summer after eruptions (1470 AD–present), linked to more frequent El Niños in the following boreal winter. Model simulations show that volcano-induced El Niño, and its associated warm pool air-sea interaction, intensifies EASM precipitation, outweighing volcanic-induced moisture deficiency. This highlights the complex interplay between external forcing and internal climate variability in shaping EASM and potential flood disasters.

Fei Liu, Chaochao Gao, Jing Chai, Alan Robock, Bin Wang, Jinbao Li, Xu Zhang, Gang Huang, Wenjie Dong