The Sunset Western Garden Book is a mainstay in the libraries of Western gardeners and you're likely to find a well-worn copy available for reference in any garden center in the West. Sunset has divided the eleven Western states into 24 climate zones.
The USDA Plant Hardiness Map provides average low temperatures for each area which will help to determine whether a plant will survive in a particular location in the winter. However, with this criteria alone, the Olympic Rain Forest is in the same zone as parts of the Sonoran Desert. The Sunset Climate Zones also take into consideration elevation, ocean influence, continental air influence, mountains and hills and local terrain to give a better picture of what plants will do well in each area.
Now Sunset has expanded the climate zones to all 50 states and have provided the information online. Information about the growing season is included for every zone, though the information is more extensive for the original Western zones.