Mountain rivers of the Western Himalaya support freshwater biodiversity that is sensitive to thermal change, but spatially continuous observations are difficult to obtain across remote terrain. We used Landsat 8 thermal observations to characterize seasonal thermal conditions within selected river corridors in Uttarakhand, Himachal Pradesh, Jammu & Kashmir, and Ladakh during 2014-2024. Four perennial, glacier-fed rivers-Alaknanda, Beas, Chenab, and Indus-were delineated from SRTM-derived drainage networks, and a 50-m corridor was used as a consistent spatial unit for extracting satellite-derived land surface temperature (LST). We quantified seasonal and interannual thermal patterns and screened temperature-based habitat suitability for 10 freshwater fish species using published thermal ranges. Summer thermal conditions increased across the study regions, with the largest reported increases of approximately 2°C over the study period in Jammu & Kashmir, Himachal Pradesh, and Uttarakhand; Ladakh remained the coldest region. Temperature-based suitability declined for several cold-water species, including Schizothorax richardsonii, Salmo trutta, and Oncorhynchus mykiss, whereas some warm-water species showed stable or slightly increasing suitable area. Pixel-level linear trends were extrapolated to 2044 as a scenario representing continuation of the observed 2014-2024 trend. The results demonstrate the value of satellite thermal observations for screening spatial and temporal changes in river-corridor thermal conditions and identifying areas where freshwater fishes may experience increasing thermal pressure. Because the analysis uses LST within a river corridor rather than direct in-water temperature measurements, the results represent the thermal component of habitat suitability and should not be interpreted as a complete assessment of fish habitat.