Washington’s Climate | Washington State Climate Office

Precipitation

The climates of western and eastern Washington are vastly different due to the state’s geography, and the Cascade Mountains are an important factor. Western Washington is greatly influenced by the ocean, and is much wetter and milder than eastern Washington. While the Cascade Mountains cause the most distinct rainshadow in the state, the Olympic Mountain range also produces a rain shadow effect. For example, Quinault, on the windward side of the Olympics, has an annual average precipitation of 151.45″ but in Sequim, only 56 miles away as the crow flies and on the leeward side, the annual average precipitation is 23.98″. A high resolution map of the average annual precipitation across Washington can be found at the PRISM Climate Group and demonstrates some of these major distinctions driven by terrain. Averaging across all of Washington state and accounting for the mountainous terrain, the average annual precipitation for the state is about 45”.

Temperature

While the temperature variations across Washington are less than the precipitation variability, there are still some important distinctions. In general, eastern Washington is colder in the winter and warmer in the summer compared to western Washington. This is because they do not have the moderating effect of the Puget Sound and the Pacific Ocean. On an annual basis, temperatures are cooler in the Olympic Mountains and Cascade Mountains, and generally cooler in eastern Washington compared to western Washington. Averaging across all of Washington state and accounting for mountainous terrain, the average annual temperature is about 47.1°F.

More Information

Different aspects of Washington’s climate are explored more in our Climate Matters feature, which are cataloged in a searchable database. More details can also be found in the Climate of Washington Narrative from the Western Regional Climate Center.

Washington is split into 10 climate divisions as defined by NOAA. Brief geographical descriptions, along with summaries written by WASCO are shown below.

	Climate Division Summaries	Description
1	Climatology of WA’s West Olympic Coast Climate Division	This division covers the entire WA coast to the west and southwest side of the Olympic Mountains, ranging in elevation from sea level to 7,969 ft on Mount Olympus, the tallest peak in the Olympic Mountains.
2	Climatology of WA’s NE Olympic- San Juan Climate Division	This division encompasses the farthest northeast portion of the Olympic Peninsula, a small western portion of Skagit county, and the entirety of Whidbey Island, Camano Island, and the San Juan Islands. It is the smallest climate division in WA, but the elevation ranges from sea level to 2,398 ft on Mt. Constitution in Orcas Island.
3	Climatology of WA’s Puget Sound Lowlands Climate Division	This division encompasses the lowlands nestled between the Olympics and the Cascades. True to its name, elevation rarely breaches 1000’, but the borders of the division that include the northeast side of the Olympic Mountains see higher elevations up to between 4,000 and 5,000 ft.
4	East Olympic Cascade Foothills	This division encompasses the eastern slopes of the Olympic Mountains and the beginning of the western slopes of the Cascade Mountains, as well as parts of southwest WA.
5	Cascade Mountains West	The Cascade Mountains include rugged terrain, the tallest peak in WA (Mt. Rainier at 14,410 ft), and alpine glaciers. The western slopes of the Cascades have higher precipitation totals compared to the eastern slopes.
6	East Slope Cascades
7	Okanogan Big Bend	This climate division includes the valleys along the Okanogan, Methow, and Columbia Rivers as well as the Okanogan highlands, with elevation varying from 1,000 ft to 3,000 ft.
8	Central Basin	This climate division encompasses the Lower Columbia Basin and is the lowest and driest division in eastern Washington.
9	Climatology of WA’s Northeast Climate Division	This division encompasses the lower elevations of the Spokane River valley but mostly includes higher elevations of the Okanogan highlands (ranging from 2,000 to 6,000 ft). The majority of the precipitation that occurs is during the winter in the form of snowfall.
10	Palouse Blue Mountains	This division encompasses the southeastern portion of the state from Spokane to the Oregon border and includes the Blue Mountains (elevation ~6,500 ft).