Southern China spring rainfall (SCSR) is significant for agricultural sowing and soil moisture accumulation before the rainy summer. A better prediction of the rainfall improves our ability to risk response to natural disasters. It is found that the SCSR can be promoted by multi‐year El Niño events through the high‐latitude pathway (HP) and low‐latitude pathway (LP). The long‐lasting El Niño warming heats the tropical troposphere persistently until the decaying spring, which strengthens the Arctic polar vortex and the mid‐latitude blockings. This HP is in favor of more southward transport of Rossby wave energy and cold air, resulting in strong ascending motions over southern China (SC) in spring. The multi‐year El Niño also induces an enhanced western North Pacific anticyclone and a secondary circulation transporting moisture to SC through the LP. The HP is more important in the early spring, while the LP dominates the heavy SCSR in the late spring.

The warm center of the 2015/2016 extreme El Niño was located further to the west compared to previous extreme events, causing vastly different social‐economic impacts. Though many studies investigated ocean‐atmosphere couplings responsible for its large magnitude, the dynamics that govern the unique structure of the event remain elusive. Here we show that a local ocean‐atmosphere feedback among convection‐induced surface winds, oceanic upwelling and sea surface temperature in the far‐eastern Pacific, resulted in a boreal summer cooling tendency along the South American coast. It canceled warming in the far‐eastern equatorial Pacific that would otherwise develop, leading to the distinctive anomaly pattern of the 2015/2016 El Niño. These processes were initially triggered by the leftover anomalous warm sea surface temperature and positive moist static energy over the northeastern tropical Pacific in the following boreal spring of the 2014 warm event.

New insight into the contribution of anomalous South China Sea (SCS) warming is proposed to understand strong southern China (SC) winter rainfall. El Niño events, which weaken the East Asian winter monsoon (EAWM), favor SC winter rainfall. However, the changes in SC winter rainfall are not always in phase with the El Niño‐Southern Oscillation, making the prediction of East Asian climate challenging. Here, we show that the increased moisture associated with the warming SCS induced by the weakening western boundary current leads to increased meridional moisture transport to SC. Particularly, during the El Niño mature winter phase, this effect works jointly with a weakened EAWM to determine an increased rainfall over SC. Therefore, we suggest that the thermal state of the SCS should be considered when large‐scale tropical ocean‐atmosphere variability is utilized to predict SC winter rainfall.