Snowmelt and related extreme events can have profound natural and societal impacts. However, the studies on projected changes in snow-related extremes across the Tianshan Mountains (TS) and Pamir regions have been underexplored. Utilizing regional climate model downscaling and bias-corrected CMIP6 data, this study examined the changes in snowmelt and water available for runoff (SMROS, rainfall plus snowmelt) during the cold seasons across these regions for historical (1994-2014) and future (2040-2060) periods under shared socioeconomic pathway (SSP) scenarios (SSP245 and SSP585). The results demonstrated that accumulated snowmelt was projected to rise by 17.98% and 20.36%, whereas SMROS could increase by 26.97% and 28.95%, respectively, under SSP245 and SSP585 scenarios. Despite relatively minimal changes in extreme snowmelt, the magnitude of the historical daily maximum extreme SMROS (10-year return level) was 28.04 mm and was expected to increase by 15.32% and 15.31% under the SSP245 and SSP585 scenarios, respectively, especially in western TS exceeding 26%. Meanwhile, areas with a daily extreme SMROS exceeding 50 mm could rise by over 13.5%. A notable rise in daily extreme SMROS and its area occupation in high intensity highlighted an increased risk of rainfall-driven extreme snowmelt events. The absolute increase in snowfall and frequent snow-rain phase transitions during the cold season under climate warming (SSP245: 2.19 degrees C and SSP585: 2.22 degrees C) benefits the increase in high-intensity rain-on-snow events, leading to extreme SMROS augmentation. The findings emphasize the significant role of rainfall-trigger snowmelt events in exacerbating extreme snowmelt in a warming climate.