Chapter 3 -West Versus East

The Cascade Mountains divide Washingtoninto two very different environments. A mild,moist climate and dense forests dominate theregion west of the mountains. To the east,however, the climate is dry and hot. There islittle vegetation other than sparse trees,sagebrush, and grasses. Because of the CascadeMountains, Washington has two environmentsas different as night and day.

As you might have guessed, western

Washington includes all areas west of theCascade Mountains. Frequent rains andmountain snowfall provide this region with anabundance of water. The rain and melted snowflow from the mountains into westernWashington’s many lakes and rivers. Thismoisture allows many types of trees and plantsto thrive in this mild, moist climate. Thus, our

state is nicknamed, “The Evergreen State.”



In contrast, the climate in eastern Washingtonis much more harsh and dry. Only scatteredtrees and vast areas of sagebrush and grassthrive here. These types of vegetation do not

require regular moisture. Of course irrigationhas made it possible for other plants and crops togrow in eastern Washington. Physical formationsof granite and basalt also dominate the region.

These features and climate have combined tocreate a hostile environment.To develop a better understanding of eachregion, we will discuss the physical features,climate, and vegetation of each in more detail.

Western Washington

Western Washington includes all areas west

of the CascadeMountain crest to the PacificOcean.

Physical Features

A great variety of physical features exist in

western Washington. Our shoreline is irregularwith numerous harbors and bays. WillapaBay,Grays Harbor, HoodCanal, and Puget Soundare some of the more well-known.

In addition to the many harbors and bays,

western Washington has numerous lakes andrivers. The lakes in this region are fed yearroundby high levels of precipitation and meltingsnow. Rivers and streams also receive much oftheir water in this fashion.

Rivers in western Washington can floodduring times of heavy rains and warmer wintertemperatures. Flooding usually happens duringthe rainy season. Floods often destroy propertyand harm communities. Although oftendangerous, floods play an important role in therenourishment of floodplains.

Mountains are easily-spotted physical

features in western Washington. The majoruplands include the Willapa Hills, the OlympicMountains, and the Cascade range and its majorvolcanoes. Some volcanic peaks can rise morethan 6,000 feet higher than the highest peaks ofthe Cascade Mountains.

When the ice from the last ice age began to

melt, the ocean rose and flooded westernWashington. The flood covered the lowlands.

This left many peninsulas and islands. The twolargest peninsulas in western Washington arethe Olympic and Kitsap peninsulas. Islands alsodot the waterways of western Washington. TheSan Juans, Bainbridge, Vashon, and Whidbeyare some of the many popular islands in thisregion.


There are two climates within the western

Washington region. They are the west coastmarine and the highland climates. The dominantclimate of the lowlands is west coast marine.

This climate has frequent rainfall throughoutmost of the year. Rainfall usually declines duringthe summer. Summer temperatures are mildwith limited humidity. Winter temperaturesremain unusually mild given our northernlatitude. This is because of our location next tothe Pacific Ocean. The ocean affects our climateby keeping the temperature more constant.

In contrast, the mountains of western

Washington have a highland climate. These areas

of western Washington have short, cool, andrainy summers. The winters are long, cold, andreceive much more snowfall than the lowlands.

The moderate temperatures and abundantmoisture in western Washington support densevegetation. Evergreen forests and deciduoustrees cover the landscape like a thick, greencarpet. The highest mountain peaks have little orno vegetation growing on their slopes. In contrast,the lowlands have roads, farms, and cities carvedfrom theorest. As the region has grown, peoplehave removed more of our forests.


A mild and wet climate allows dense standsof vegetation to grow in western Washington.The thick canopy of evergreen trees providesshade for the plants on the forest floor. Hemlock,cedar, spruce, alder, and maple trees providehabitats for animals and other plants in ourforests. Without a doubt, the vegetation inwestern Washington is very unique!

The abundant moisture and the shade of thecanopy allow only certain types of plants togrow. Rhododendrons, azaleas, ferns, andmosses all grow well in this climate. Mushroomsalso thrive in the shaded environment. Some ofthe finest mushrooms in the world grow on ourforest floors. Before you ever pick or eat amushroom, make sure it is not poisonous.

Other areas of the forest have been cleared

by logging or fire. Alder, ash, and maple treesgrow well in the forest clearings. River valleyswhere sunlight is common also make good homesfor these trees. The river valleys and flood plainsare great locations for farms. Farmers can groweverything from flower bulbs to cranberries.


Western Washington may be divided intothree subregions. Each subregion has its ownunique physical features, climate, and vegetation.

How do these regions differ from one another?

Coastal Subregion

The coastal subregion is a beautiful area of

Washington. Mountains, bays, peninsulas, andeven a rain forest are found here. This area has avery moderate climate with dense vegetation.People live in small communities and depend on

the natural resources of this region.

Physical Features

Coastal mountains rise throughout the long,narrow coastal subregion. The Olympics are thisregion’s most notable mountains. These ruggedmountains rise nearly 8,000 feet above the Pacific.

Glaciers can be found on the higher peaks. Themountainous terrain is also home to many alpinelakes. The rugged terrain makes these smalllakes difficult to access.

Precipitation and melting snow providewater for many short rivers. They flow into thePacific and its many bays and harbors. WillapaBay and Grays Harbor are just two of the largestin the subregion. The largest river in Washington,the Columbia, forms the southern boundary ofthe coastal subregion.


The coastal subregion has only two climates.These climates are the west coast marine and thehighland climates. The higher elevations in theOlympic Mountains have a highland climate.

Rain and snow fall much of the year. In some ofthe higher, shaded elevations, glaciers slowlymove down the steep mountain slopes.

The lower elevations of the coastal subregionare subjected to the west coast marine climate.The abundant moisture and mildtemperaturesare perfect for the dense vegetation that growshere. In fact, the only temperate rain forest in thelower 48 states is located here! The Hoh rainforest is a beautiful place to visit. There you cansee trees more than 500 years old.


Dense stands of trees cover much of this

coastal subregion. Hemlock, cedar, and spruceprovide a thick evergreen canopy. This canopyallows little sunlight to reach the forestfloor. Moss, ferns, nettles, lupines, lichens,rhododendrons, and thousands of other plantsthrive in the shaded areas.

Giant trees such as Sitka spruce, hemlock,

and western red cedar have fallen and crisscross

the forest floor. These fallen giants allow light tobathe the forest floor where they once stood. Thelight and nutrients from the decomposing woodallow a variety of new plants to thrive in thevacant area. The seedlings of the cedar andspruce grow quickly reaching for the light withthe hope that someday they will be a giant.

However, people have invaded this pristine

region of our state to harvest the timber from the

forest. Loggers clear-cut giant cedar and sprucetrees and left only the hemlocks. Hemlocks thrive

in the shade of the forest. Exposed to the sunlight,

seedlings grow quickly. The hemlocks remain as

proud reminders of the original forest thatthrived in this region for centuries.

New plants and vegetation eventuallyreplaced the natural forest. Alder trees, whichonce lived only along the beaches, spread inland.Raspberries and blackberries, in a bath of light,

spread in every direction. Eventually the loggersrealized that the hemlock was valuable not forits wood, but instead for its sap. The large giants’sap provides rayon for plastics. Hemlocks, thelast trees remaining, were cut as fast as the othertrees in our forest.

Fortunately the hemlock, spruce, and cedar

can thrive in the protected areas of our national

parks and wilderness areas. Hopefully, plant

and animal habitats will be restored as they were

just 100 years ago.

Western Lowlands Subregion

The western lowlands subregion is clearly

one of the most beautiful and diverse regions inour state. The lowlands have numerous hills,streams, rivers, lakes, and much more to offer.

The weather is mild in both the summer and

winter months. Moisture keeps the trees, grasses,

and other plants green year-round.

Physical Features

The western lowlands is a complex area dueto the erosion from glaciers and water. Its most

important physical feature is Puget Sound. Thiswaterway extends south from Everett toOlympia. Puget Sound, HoodCanal, and theStrait of Juan de Fuca form the major inlandwaterways of western Washington.

Long ago, as the glaciers melted and retreatednorth, rising sea level flooded the interior

lowlands of western Washington. The watercovered all the land except only the highestportions of the hills and mountains. These

uncovered pieces of land became the islands and

peninsulas in western Washington.

The Olympic and Kitsap peninsulas, and

Whidbey, Bainbridge, Vashon, Mercer and the

San Juan islands are important physical features

in the western lowlands. The protectedwaterways provide excellent ports and shippinglanes. Ocean-going vessels can travel into thelowland region and safely off-load their cargo.

Rivers and streams also flow from the nearbyCascade and Olympics mountains into the

lowlands. From the Columbia in the south to the

Nooksack north of Bellingham, there arehundreds of rivers in this region. These riversare fed by heavy rainfall and melted snow. Theyfrequently flood and deposit their fertile silt onthe floodplains.


The western lowlands has only one type of

climate, the west coast marine. This subregionreceives plenty of rainfall and an occasionalsnowfall each year. Most areas receive 40 to 60

inches of precipitation each year.

The Pacific Ocean maintains the mildtemperatures. They tend to be mild throughoutthe year. Summers are very comfortable becauseof the mild temperatures and infrequent rain.Temperatures occasionally reach the upper 80sand low 90s, but normally they range from 65 to

85 degrees.

Winter weather is also mild but very wet.

The lowlands receive most of its rain in thewinter months and early spring. Temperaturesare comfortable because of the influence of thePacific. Winter temperatures are rarely extreme,or below zero, for long periods. An occasionalstorm, blowing in from the north Pacific, maybring snow and subfreezing temperatures to thelowlands. When these storms hit, they rarely lastmore than three to five days.


The natural vegetation in the westernlowlands is mainly made up of conifer anddeciduous forests. These thick forests aredifferent from those of the coast. The conifers inthis region, in contrast, are smaller than theircousins in the Olympics. Douglas fir, westernred cedar, western hemlock, and Sitka spruce allgrow in the western lowlands subregion.

Deciduous trees also grow well in the mildand wet climate. Alder, maple, and oak trees linethe banks of the rivers and grow around theflood plains. Other plants and shrubs grow quitewell in the forest. Rhododendrons, lupine,azaleas, ferns, and berries are common in thelowlands.However, human activity has greatlychanged the natural vegetation. People havecleared the forests for roads, communities, andfactories. Domesticated plants and trees havereplaced some of the original vegetation of thelowlands.

Western Cascades Subregion

The Cascade subregion of westernWashington is located west of the CascadeMountain crest. This region includes the western

slopes, or windward side, of the Cascades from

Canada to the Columbia River.

Physical Features

The most obvious feature of the western

Cascades subregion is the Cascade Mountains.

The Cascades extend more than 600 miles from

British Columbia, Canada to northern California.

Glaciers and deep snow dominate the ruggednorth Cascades. Mount Baker is the only majorvolcanic peak in this area. However, the NorthCascades have hundreds of jagged granite spiresjutting skyward.

As you travel south through the subregion,

the mountains become less dominant in heightbut are still very beautiful. Volcanic peaks nowdominate the mountain skyline. Two majorvolcanoes, Mount Rainier and Mount St. Helens,

are in this region. Mt.Rainier, the tallest peak, is

14,411 feet tall. It stands more than 6,000 feet

higher than any of the surrounding mountains.

The subregion is also home to many alpinelakes, streams, and rivers. The water flowinginto them once fell as either rain or snow. Themelting snow and running rain water collect inthe valleys and continues its journey to the ocean.


The western slope of the CascadeMountainshas a highland climate above 3,000 feet. Thelower elevation has a west coast marine climate.The highland climate can change very quickly.As storms push in from the Pacific, thick clouds

form and release heavy rain or snow.

The windward location of the western

Cascade subregion causes heavy precipitation.

The heaviest precipitation, both rainfall and

snowfall, occurs from early October to late April.

Annual snow pack can be as much as 30 to 90 feet

in places.


Evergreen forests blanket the western slopesof the western Cascade subregion. The higherelevations are usually void of trees. Only shrubs,low lying plants, and mosses can survive thecooler temperatures and heavy snows. The

warmth of late spring and early summer bringsa variety of alpine flowers and grasses into bloom.

The area above where trees can grow is knownas the tree line. You can see the natural tree lineon many of the higher peaks in the Cascades.

Eastern Washington

Eastern Washington is the second major

geographical region in our state. This large region

includes all the land east of the CascadeMountain

crest to the Idaho and Oregon borders. Theregion of eastern Washington is very differentfrom the western Washington region.

Eastern Washington has less precipitation,

extreme temperatures, and very few trees.Grasses and sagebrush cover much of the area.The drier climate is a direct result of therainshadow effect. Please review page 29 if youwould like to learn more about this climaticfeature.

Physical Features

Many unique physical features are found

within the eastern Washington region. Thesefeatures include the eastern Cascades, theOkanoganHighlands, the Rockies, and the Blue

Mountains. The rolling hills of the Palouse andthe Columbia Plateau are other impressivelandforms. Fire and ice helped to form thesephysical features.

Although the climate is very dry throughoutthe year, the region has several major rivers andlakes. Lake Chelan, MosesLake, the Potholes,and Franklin D. Roosevelt Lakeare large andpopular freshwater lakes. There are also manyalpine and glacial lakes in the mountain areas.

Two volcanic peaks dominate the eastern

Cascade Mountains. One, Glacier Peak, is rarely

seen unless you are at a high vantage point. Ittowers above the North Cascades in easternWashington. MountAdamsin southernWashington is the last of the major volcanicpeaks in our state.

The winter snow melt of the Cascade, Rocky,and Blue mountains fills the many rivers in theregion. The Columbia River is the main riverthat flows through eastern Washington. The

Columbia starts its journey to the Pacific Oceanin British Columbia, Canada. Every other majorriver in eastern Washington is a tributary of theColumbia. A tributary is a river that flows intoa larger river before reaching the ocean. Thetributaries also carve the region’s numerous rivervalleys.


The eastern Washington region has only twomajor types of climate; semiarid and highland.

The region does not receive much precipitation.

The Cascades prevent the moisture from reaching

the region. The surrounding mountains severelyreduce the amount of moisture the regionreceives. The eastern slope of the Cascadesreceives no more than 15 to 30 inches of moistureeach year. It continues to decline the farther eastyou travel until you reach the foothills of theRocky Mountains.