This map shows predicted percent change in precipitation for the year 2080 under a medium-high green house gas emissions scenario (A2). The data is the average of 16 different climate model predictions for the year 2080 and is available for download from TNC’s climatewizard.org.
Generally, dry areas will get dryer and many wet areas will get wetter. Most of California and the southwestern US will become drier. Forest fires will rage and some plants and animals will be driven to extinction.