Just as the geography of the West is varied, so too is the availability of water. Some areas in the West receive very little precipitation. These locations in the semiarid or arid climate regions may receive less than 10 inches of rain each year. Plans like cacti, sagebrush, grass, and some shrubs that can withstand high heat live in these regions.

Other areas in the West receive a lot of rainfall. Seattle, Washington averages about 40 inches of rain every year. The coastal parts of California are home to large forests full of trees that enjoy high levels of precipitation. Located in the Pacific Ocean, Hawaii has a wet, tropical climate. Rainforest plants and animals can be found in the state. In northern Alaska, the tundra is a dry plain that supports only grasses in the summer when the top soil thaws.