Western Washington also is home of the Olympic Mountains, far west on the Olympic Peninsula, which supports dense forests of conifers and areas of temperate rainforest. These deep forests, such as the Hoh Rainforest, are among the only temperate rainforests in the continental United States.[9]
In contrast, Eastern Washington, east of the Cascades, has a relatively dry climate with large areas of semiarid steppe and a few truly arid deserts lying in the rain shadow of the Cascades; the Hanford reservation receives an average annual precipitation of 6 to 7 inches (150 to 180 mm). Farther east, the climate becomes less arid, increasing as one goes east to 21.2 inches (540 mm) in Pullman.[10] The Okanogan Highlands and the rugged Kettle River Range and Selkirk Mountains cover much of the northeastern quadrant of the state. The Palouse southeast region of Washington was grassland that has been mostly converted into farmland, and extends to the Blue Mountains.