Cattle production capacity on western rangelands is potentially vulnerable to climate change through impacts on the amount of forage, changes in vegetation type, heat stress, and year-to-year forage variability. The researchers in this study projected climate change effects to rangelands through the year 2100 and compared them to a present-day baseline to estimate vulnerability of cattle operations. The analysis predicted an increase in forage quantity in northern regions, a move from woody dominance toward grassier vegetation types overall but with considerable variability between areas, a substantial increase in the number of heat-stress days across all regions beginning as early as 2020–2030, higher year-to-year variability of forage quantity for most regions. All four factors combined to predict declining grazing capacity in southwestern regions. In northern and interior regions of the West, the benefits of increased forage are mostly offset by increases in heat stress and forage variability. The predicted increased vulnerability of cattle production in the Southwest provides strong impetus for adaptation by livestock producers and public land managers in anticipation of these changes. This study can be used by range managers to begin to think about long-term planning and communication with stakeholders (such as grazing permit holders) about what kinds of conditions to expect in the future.