The relationship between the summer northernmost position of southerly wind and precipitation over East China is investigated. The northern limit of summer southerly wind index (NLSSWI) over East China is defined as the latitude where the longitude-averaged (105–120°E) low-level meridional wind is equal to zero. Results show that there is a significant negative (positive) correlation between NLSSWI and summer precipitation over the Yangtze River (North China) region. Thus, the proposed NLSSWI may have implications for the prediction of summer precipitation anomalies in these regions. In positive NLSSW index years, a cyclonic circulation anomaly is observed over the tropical western North Pacific and an anticyclonic circulation anomaly is seen over the subtropics of East China, accompanied by southerly anomalies over East China. This leads to above-normal moisture penetrating into the northern part of East China. In addition, significant upward (downward) motion anomalies can be found over the North China (Yangtze River) region. As a result, there are significant positive (negative) precipitation anomalies over the North China (Yangtze River) region. Further examination shows that sea surface temperature anomalies over the tropical eastern Pacific and Indian Ocean both contribute to the formation of NLSSWI-related circulation anomalies over the tropical western North Pacific.