Snow cover area (SCA) and snow water equivalent (SWE) are critical variables for understanding water resource status and river flows from snowmelt in mountainous regions. This study investigated the long-term spatial and temporal variations of SCA and SWE over the 2000–2025 period in Razavi Khorasan Province, Iran, utilizing MODIS satellite data and the FLDAS in the Google Earth Engine (GEE). To evaluate the accuracy of the results, the estimated data were validated against field measurements from snow-gauge stations. The satellite-derived estimates were evaluated using statistical metrics, including linear correlation (R), root mean square error (RMSE), mean absolute error (MAE), and bias. Furthermore, the SWE-to-precipitation ratio (SPR) index was calculated to investigate long-term changes in the contribution of snowfall to total precipitation. The annual Standardized Precipitation Index (SPI) was also employed to analyze the relationship between SCA and SWE, with drought and wet events. The results indicated that the maximum snow cover areas occurred in 2005 and 2008, 10775.7 km2 and 6697.7 km2, respectively. Conversely, the minimum snow cover area was recorded in 2018 at 632.4 km2. The overall trend of both SCA and SWE in the study area was downward. The negative slope of trend revealed a significant annual decrease of approximately -31.9 km2/year in snow cover area (at the 5% statistical significance level). The long-term SPR index also exhibited a decreasing trend with a slope of -0.0004/year, indicating a declining share of snowfall relative to total precipitation in the region.