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This study investigates Meiyu (June‐July) rainfall from 1980 to 2000 over Yangtze‐Huaihe River valley (YHRV) and reveals a decadal change around 1991 with a seesaw‐like distribution. This decadal change is closely associated with negative phase of preceding winter El Niño–Southern Oscillation (ENSO) Modoki (EM) in the pre‐1991 epoch and positive phase of conventional ENSO (CE) in the post‐1991 epoch. In response to negative EM (pre‐1991 epoch), the source of water vapor is western North Pacific, associated with the eastward retreat of western Pacific subtropical high (WPSH) and the northward shift of East Asian westerly jet (EAWJ). On the other hand, in response to positive CE (post‐1991 epoch), water vapor generally comes from the South China Sea, associated with the enhancement and westward advance of the WPSH and southward shift of the EAWJ. Two possible mechanisms are proposed …