of
Westport Washington is the northwesternmost state of the
contiguous United States. It borders
Idaho to the east, bounded mostly by the meridian running north from the confluence of the
Snake River and
Clearwater River (about 117°02'23" west), except for the southernmost section where the border follows the Snake River. Oregon is to the south, with the Columbia River forming the western part and the 46th parallel forming the eastern part of the Oregon–Washington border. During Washington's partition from Oregon, the original plan for the border followed the Columbia River east until the confluence with the Snake, and then would have followed the Snake River east; this was changed to keep
Walla Walla's fertile farmland in Washington. To the west of Washington lies the Pacific Ocean. Its northern border lies mostly along the
49th parallel, and then via marine boundaries through the
Strait of Georgia,
Haro Strait, and
Strait of Juan de Fuca, with the
Canadian province of
British Columbia to the north. Washington is part of a region known as the
Pacific Northwest, a term which always refers to at least Washington and Oregon, and may or may not include some or all the following, depending on the user's intent: Idaho, western
Montana,
northern California, British Columbia, and
Alaska. The high mountains of the
Cascade Range run north–south, bisecting the state. In addition to
Western Washington and
Eastern Washington, residents call the two parts of the state the "Westside" and the "Eastside", "Wet side" and "Dry side", or "Timberland" and "Wheatland", the latter pair more commonly in the names of region-specific businesses and institutions. These terms reflect the geography, climate, and industry of the land on both sides of the Cascades.
Western Washington From the
Cascade Mountains westward,
Western Washington has a mostly
Mediterranean climate, with mild temperatures and wet winters, autumns and springs, and relatively dry summers. The Cascade Range has several
volcanoes, which reach altitudes significantly higher than the rest of the mountains. From north to south, these major volcanoes are
Mount Baker,
Glacier Peak,
Mount Rainier,
Mount St. Helens, and
Mount Adams. All are active volcanoes. Mount Rainier—the tallest mountain in the state—is south of the city of Seattle, from which it is prominently visible. The
United States Geological Survey considers Mount Rainier the most dangerous volcano in the Cascade Range, due to its proximity to the
Seattle metropolitan area, and most dangerous in the continental U.S. according to the
Decade Volcanoes list. It is also covered with more
glacial ice than any other peak in the contiguous 48 states. 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. These deep forests, such as the
Hoh Rainforest, are among the only rainforests in the continental United States. While Western Washington does not always experience a high amount of rainfall as measured in total inches of rain per year, it does consistently have more rainy days per year than most other places in the country.
Eastern Washington Eastern Washington—the part of the state east of the Cascades—has a relatively dry climate, in distinct contrast to the west side. It includes large areas of semiarid
steppe and a few truly arid
deserts in the
rain shadow of the Cascades; the Hanford reservation receives an average annual precipitation of . Despite the limited amount of rainfall,
agriculture is an extremely important business throughout much of Eastern Washington, as the soil is highly productive and
irrigation, aided by dams along the Columbia River, is fairly widespread. The spread of population in Eastern Washington is dominated by access to water, especially rivers. The main cities are all located alongside rivers or lakes; most of them are named after the river or lake they adjoin. Farther east, the climate becomes less arid, with annual rainfall increasing as one goes east to in Pullman, near the Washington–Idaho border. The
Okanogan Highlands and the rugged
Kettle River Range and
Selkirk Mountains cover much of the state's northeastern quadrant. The
Palouse southeast region of Washington was grassland that has been mostly converted into farmland, and extends to the
Blue Mountains.
Climate of Washington, using 1991–2020
climate normals. caused a large
dust storm in arid parts of Eastern Washington on October 4, 2009. Courtesy: NASA/GSFC, MODIS Rapid Response. The state of Washington has a temperate climate. The eastern half of Washington has a
semi-arid to
warm-summer mediterranean climate, while the western side of Washington as well as the coastal areas of the state have a cool
oceanic climate or warm-summer mediterranean climate. Major factors determining Washington's climate include the large semi-permanent
low pressure and
high pressure systems of the north Pacific Ocean, the continental air masses of North America, and the Olympic and Cascade mountains. In the spring and summer, a high-pressure
anticyclone system dominates the north Pacific Ocean, causing air to spiral out in a clockwise fashion. For Washington, this means
prevailing winds from the northwest bring relatively cool air and a predictably
dry season. In the autumn and winter, a low-pressure
cyclone system, the
Aleutian Low, takes over in the north Pacific Ocean. The air spiraling inward in a counter-clockwise fashion causes Washington's prevailing winds to come from the southwest, and bring cool and overcast weather and a predictably
wet season. The term "
Pineapple Express" is used colloquially to describe
atmospheric river events, where repeated storm systems are directed by this persistent cyclone from the tropical Pacific regions a great distance into the Pacific Northwest. Western Washington is very cloudy during much of fall, winter, and early spring.
Seattle averages the fewest sunshine hours of any major city in the United States. Despite Western Washington's marine climate similar to many coastal cities of Europe, there are exceptions such as the "Big Snow" events of 1880, 1881, 1893, and 1916, and the "deep freeze" winters of 1883–1884, 1915–1916, 1949–1950, and 1955–1956, among others. During these events, Western Washington experienced up to of snow, sub-zero (−18 °C) temperatures, three months with snow on the ground, and lakes and rivers frozen over for weeks. The
Southern Oscillation greatly influences weather during the cold season. During the El Niño phase, the jet stream enters the U.S. farther south through California, therefore late fall and winter are drier than normal with less snowpack. The La Niña phase reinforces the jet stream through the Pacific Northwest, causing Washington to have more rain and snow than average. In 2006, the Climate Impacts Group at the
University of Washington published ''The Impacts of Climate Change in Washington's Economy'', a preliminary assessment of the risks and opportunities presented given the possibility of a rise in global temperatures and their effects on Washington state.
Rain shadow effects Rainfall in Washington varies dramatically going from east to west. The Olympic Peninsula's western side receives as much as of precipitation annually, making it the wettest area of the 48 conterminous states and a
temperate rainforest. Weeks may pass without a clear day. The western slopes of the Cascade Range receive some of the heaviest annual snowfall (in some places more than water equivalent) in the country. In the rain shadow area east of the Cascades, the annual precipitation is only . Precipitation then increases again eastward toward the Rocky Mountains (about east of the Idaho border). The Olympic mountains and Cascades compound this climatic pattern by causing
orographic lift of the air masses blown inland from the Pacific Ocean, resulting in the windward side of the mountains receiving high levels of precipitation and the leeward side receiving low levels. This occurs most dramatically around the Olympic Mountains and the Cascade Range. In both cases, the windward slopes facing southwest receive high precipitation and mild, cool temperatures. While the Puget Sound lowlands are known for clouds and rain in the winter, the western slopes of the Cascades receive larger amounts of precipitation, often falling as snow at higher elevations.
Mount Baker, near the state's northern border, is one of the snowiest places in the world. In 1999, it set the world record for snowfall in a single season—. East of the Cascades, a large region experiences strong rain shadow effects. Semi-arid conditions occur in much of Eastern Washington with the strongest rain shadow effects at the relatively low elevations of the central
Columbia Plateau—especially the region just east of the Columbia River from about the Snake River to the
Okanagan Highland. Thus, instead of rain forests, much of Eastern Washington is covered with dry
grassland,
shrub-steppe, and
dunes.
Temperatures The average annual temperature ranges from on the Pacific coast to in the northeast. The lowest temperature recorded in the state was in
Winthrop and
Mazama. The highest recorded temperature in the state was at
Hanford on June 29, 2021. Both records were set east of the Cascades. Western Washington is known for its mild climate, considerable fog, frequent cloud cover, long-lasting drizzles in the winter and warm, temperate summers. The eastern region, which does not benefit from the general moderating effect of the Pacific Ocean, occasionally experiences extreme climate. Arctic cold fronts in the winter and heat waves in the summer are not uncommon. In the Western region, temperatures have reached as high as in
Maple Valley during the
June 2021 heat wave, and as low as in
Longview, and even in
Sammamish.
Flora and fauna graze at Deer Park in
Olympic National Park Forests cover about half the state's land area, mostly west of the northern Cascades. Approximately two-thirds of Washington's forested area is publicly owned, including 64 percent of federal land. Common trees and plants in the region are
camas, Douglas fir, hemlock,
penstemon, ponderosa pine,
western red cedar, and many species of ferns. The state's various areas of wilderness offer sanctuary, with substantially large populations of shorebirds and marine mammals. The Pacific shore surrounding the
San Juan Islands is heavily inhabited by
killer, gray, and humpback whales. Because of the wide range of geography, the state of Washington is home to several different ecoregions, which allow for a varied range of bird species. This range includes raptors, shorebirds, woodland birds, grassland birds, ducks, and others. There have also been a large number of species introduced to Washington, dating back to the early 18th century, including horses and burros. The
channel catfish,
lamprey, and
sturgeon are among the 400 known
freshwater fishes. Along with the Cascades frog, there are several forms of snakes that define the most prominent
reptiles and amphibians. Coastal bays and islands are often inhabited by plentiful amounts of shellfish and whales. There are five species of
salmon that ascend the Western Washington area, from streams to spawn. Washington has a variety of
National Park Service units. Among these are the
Alta Lake State Park,
Lake Roosevelt National Recreation Area,
San Juan Islands National Wildlife Refuge, as well as three national parks—the
Olympic National Park,
North Cascades National Park, and
Mount Rainier National Park. The three national parks were established between 1899 and 1968. Almost 95 percent (876,517 acres, 354,714 hectares, 3,547.14 square kilometers) of Olympic National Park's area has been designated as wilderness under the
National Wilderness Preservation System. Additionally, there are 143
state parks and9
national forests, run by the
Washington State Park System and the
United States Forest Service. The
Okanogan National Forest is the largest national forest on the
West Coast, encompassing . It is managed together as the Okanogan–
Wenatchee National Forest, encompassing a considerably larger area of around .
Administrative divisions There are 39 counties within the state, and 281 incorporated municipalities which are divided into cities and towns. The majority of the state's population lives within Western Washington, in the Seattle metropolitan area; the city of Seattle is the principal city of the metropolitan area, and Western Washington, with a 2020 census population of 737,015. ==Demographics==