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.The remainder of the state consists of: deep temperate rainforests in the west; mountain ranges in the west, central, northeast and far southeast; and a semi-arid basin region in the east, central, and south, given over to intensive agriculture.Washington is the second most populous state on the West Coast and in the Western United States, after California.This causes Washington's prevailing winds, the Chinooks, to come from the southwest, bringing relatively warm and moist air masses and a predictably wet season.
Farther east, the climate becomes less arid, with annual rainfall increasing as one goes east to 21.2 inches (540 mm) in Pullman, near the Washington-Idaho border.
In addition to Western Washington and Eastern Washington residents call the two parts of the state the "West side" and "East side", "Wet side" and "Dry side", or "Timberland" and "Wheatland", the latter pair more commonly in the names of region-specific businesses and institutions.
From the Cascade Mountains westward, Western Washington has a mostly marine west coast climate, with mild temperatures and wet winters, autumns and springs, and relatively dry summers. Western Washington also is home of the Olympic Mountains, far west on the Olympic Peninsula, which support dense forests of conifers and areas of temperate rainforest.
Mount Rainier, an active stratovolcano, is the state's highest elevation at almost 14,411 feet (4,392 m) and is the most topographically prominent mountain in the contiguous United States. Its rugged surface is rich in stands of Douglas fir, hemlock, ponderosa pine, white pine, spruce, larch, and cedar.
The state is the biggest producer of apples, hops, pears, red raspberries, spearmint oil, and sweet cherries, and ranks high in the production of apricots, asparagus, dry edible peas, grapes, lentils, peppermint oil, and potatoes.It borders Idaho to the east, bounded mostly by the meridian running north from the confluence of the Snake River and Clearwater River (about 116°57' west), except for the southernmost section where the border follows the Snake River.