A warming climate threatens the habitat of marmots. Montane ecosystems may be especially sensitive to weather anomalies because of complex abiotic and biotic interactions that arise from climate-driven reductions in snowpack. Snowpack not only provides insulation from extreme cold, but also influences forage availability through timing of melt-off and water availability. Marmot abundance declined by 69% between 2007 and 2016, and the most-severe losses occurred at warm, dry sites. Moisture was important in statistical models that included the interactions of vapor pressure deficit with cold exposure marmots. These results indicate that weather extremes, warming temperatures, and increasing aridity can lead to rapid loss of species in montane ecosystems.