Rain belts in East Asia frequently pose threats to human societies and natural systems. Advances in a skillful forecast on heavy precipitation require a deeper understanding of the preconditioned environments and the hydrologic cycle. Here, we disentangle 15 dominant moisture channels along four corridors reaching the Somali Jet, South Asia, Bay of Bengal, and Pacific basin for the warm-season rain belts. Among them, the Somali and South Asian channels were underappreciated in the literature. The results also highlight the importance of terrestrial moisture sources, and the close relationship between the moisture pathways and rain belts’ characteristics. Back-tracing the weather within a 2-week lead time reveals the pre-existing weather systems and circumglobal wave trains, that govern the moisture channels. Findings from this work develop a better understanding of East Asian rain belts’ water cycle, and may offer insights into model evaluation and heavy rainfall prediction at a longer lead time.

东亚的雨带经常对人类社会和自然系统构成威胁。对强降水的熟练预报需要对预处理环境和水文循环有更深入的了解。在这里，我们沿着四个走廊解开了15条主要的水分通道，这些走廊到达了索马里急流，南亚，孟加拉湾和太平洋盆地，成为暖季雨带。其中，索马里和南亚的渠道在文献中未得到充分重视。结果还突出了陆地水分来源的重要性，以及水分途径与雨带特征之间的密切关系。在 2 周的提前期内回溯天气，揭示了控制水分通道的预先存在的天气系统和环绕全球的波列。