Abstract: China’s northern Xinjiang is located in a typical inland arid and semiarid area where anomalous precipitation plays a significant role. In recent years, anomalous precipitation events have increased with the increase in global temperatures. In this study, the interdecadal variability of wintertime precipitation in northern Xinjiang is investigated using the observational rainfall data of 40 stations and the ECMWF ERA-Interim and NCEP/NCAR reanalysis datasets for 1979–2017. This study discusses the water vapor transport characteristics of wintertime snowstorm days and the possible mechanisms in four regions based on the HYSPLIT v4.9 model. Our main results are as follows: (1) The west boundary input of water vapor is mainly in each region, but a small amount of water vapor is imported from the northern boundary in western Tianshan, and some water vapor is imported from the southern boundary in the upper part of Tianshan. (2) The water vapor passages are mainly located in Eurasia, with the mid-latitude westerlies in the north, west, and western Tianshan; however, their exact locations are different. The water vapor transport mainly comes from the Mediterranean and the Black Sea in the north, with a contribution ratio of 58.8%; southwest of the Caspian Sea in the west, with a contribution ratio of 70.8%; the Black Sea and the southeast of the Caspian Sea in western Tianshan, with a contribution ratio of 72.9%; and India and Iran, with a contribution ratio of 64.2%. (3) The geopotential height anomaly shifts from “+” to “−” from south to north and from “−” to “+” and back to “−” from west to east in the different regions; however, the intensity, range, and location of the anomaly center are different, leading to differences in the influential regions.