By the end of the century, average annual precipitation is projected to decrease substantially in the southern half of the Southwest. Some areas would receive more precipitation as rain instead of snow.

There is uncertainty between different climate scenarios for future precipitation projections in the Southwest. Generally, there is a south-to-north gradient in annual precipitation projections, with decreases projected from central California, Nevada, Utah, and Colorado to the south. Decreases are largest in southern California, Arizona, and New Mexico (3-12%). The northern half of the region is projected to experience no change or a slight (0-3%) increase in annual precipitation. Precipitation decreases appear more likely for spring and summer months across the entire region, while winter months may experience slightly increased precipitation. Much of the mountain area in California with winters currently dominated by snow would begin to receive more precipitation as rain and then only rain by 2050. Colder and higher areas in the intermountain West would also receive more rain in the fall and spring but continue to receive snow in the winter at the highest elevations.