Abstract: The western edge of the Hengduan mountains (WHDM) is one of the regions in China with the earliest onset of the rainy season, with spring precipitation amounts at some stations even surpassing summer totals. Using high-density station-rainfall data and the European Centre for Medium-Range Weather Forecasts fifth-generation reanalysis products, the detailed spatial extent of spring precipitation over the WHDM is analyzed, and the possible causes of regional differences in spring precipitation characteristics are discussed. The typical spring precipitation region (W) over the WHDM is located in the Nujiang River Valley in Yunnan province and between 26.57°N and 27.8°N. In this region, the rainy season begins in the 9th pentad (mid-February) and can last for over 8 months. The annual precipitation peak occurs before April, with spring rainfall accounting for a larger proportion than summer rainfall. The rainy seasons start before April in the eastern region (E) and the southern region (S), which are adjacent to the region W of spring rain stations. However, their annual rainfall is dominated by summer precipitation. Further analysis shows that the precipitation difference between regions E and W is likely affected by the dynamic background difference caused by topography and the westerly in early spring, and also the difference in water vapor conditions driven by the southerly flux in late spring. The difference in precipitation between regions S and W may be mainly due to differences in water vapor conditions brought by the meridional wind circulations. In addition, the difference in vertical uplift motion induced by the local topography likely provides a crucial supplementary contribution to the observed precipitation difference.