Observed climate changes in the Western Mountains and Forests bioregion include increased seasonal, annual, minimum, and maximum temperatures, altered precipitation patterns, and a shift toward earlier timing of peak runoff. These climatic changes have resulted in widespread mortality in western forests, species range shifts and changes in phenology, productivity, and distribution of species, and an increase in wildfire severity, intensity, maximum fire size, and area burned. Predicted regional changes include an increase in average temperature of around 0.3 C per decade over the next 50 years, dramatically reduced snowpack accumulation in western mountains, and commensurate reductions in runoff and natural water storage. Ecological changes likely to result from these climatic changes include continued shifts in species phenology, productivity, and distributions, species extinctions, increased frequency, size, and duration of wildfires, increased drought length and severity, and range expansion of forest pests and pathogens.