Fine-scale characteristics of summer precipitation over Cang Mountain, a long and narrow mountain with a quasi-north–south orientation in Southwest China, are studied using station and radar data. Three kinds of rainfall processes are classifified according to the initial stations of regional rainfall events (RREs) by utilizing minute-scale rain gauge data. RREs initiating in the western part of Cang Mountain exhibit eastward evolution and tend to reach their maximum rainfall intensity on the mountaintop. The results indicate differences in the precipitation evolution characteristics between short-duration (1–3 h) and long-duration (at least 6 h) events. Short-duration events begin farther from the mountaintop and then propagate eastward, whereas long-duration events remain longer around the mountaintop. RREs that initiate from the eastern part of Cang Mountain display westward propagation and frequently reach their maximum rainfall intensity over the eastern slope of the mountain. Among them, short-duration events tend to propagate farther west of Cang Mountain at high speeds, but the westward evolution of long-duration events is mainly confifined to the eastern part of Cang Mountain. For mountaintop-originated RREs, precipitation quickly reaches its maximum intensity after it starts and then continues for a long time around the mountaintop during the period from late afternoon to early morning. These fifindings provide references for the fifine-scale prediction of precipitation evolution in small-scale mountainous areas.