Chapter 3 -West Versus East
The Cascade Mountains divide Washington
into two very different environments. A mild, moist
climate and dense forests dominate the region west
of the mountains. To the east, however, the climate
is dry and hot. There is little vegetation other than
sparse trees, sagebrush, and grasses. Because of
the Cascade Mountains, Washington has two
environments as different as night and day.
As you might have guessed, western
Washington includes all areas west of the Cascade
Mountains. Frequent rains and mountain snowfall
provide this region with an abundance of water.
The rain and melted snow flow from the mountains
into western Washington’s many lakes and rivers.
This moisture allows many types of trees and
plants to thrive in this mild, moist climate. Thus, our
state is nicknamed, “The Evergreen State.”
NW NE
SW SE
In contrast, the climate in eastern
Washington is much more harsh and dry. Only
scattered trees and vast areas of sagebrush and
grass thrive here. These types of vegetation do not
require regular moisture. Of course irrigation has
made it possible for other plants and crops to grow
in eastern Washington. Physical formations of
granite and basalt also dominate the region.
These features and climate have combined
to create a hostile environment. To develop a better
understanding of each region, we will discuss the
physical features, climate, and vegetation of each
in more detail.
Western Washington
Western Washington includes all areas west
of the Cascade Mountain crest to the Pacific
Ocean.
Physical Features
A great variety of physical features exist in
western Washington. Our shoreline is irregular with
numerous harbors and bays. Willapa Bay, Grays
Harbor, Hood Canal, and Puget Sound are some of
the more well-known.
In addition to the many harbors and bays,
western Washington has numerous lakes and
rivers. The lakes in this region are fed year round
by high levels of precipitation and melting snow.
Rivers and streams also receive much of their
water in this fashion.
Rivers in western Washington can flood
during times of heavy rains and warmer winter
temperatures. Flooding usually happens during the
rainy season. Floods often destroy property and
harm communities. Although often dangerous,
floods play an important role in the renourishment
of floodplains.
Mountains are easily-spotted physical
features in western Washington. The major uplands
include the Willapa Hills, the Olympic Mountains,
and the Cascade range and its major volcanoes.
Some volcanic peaks can rise more than 6,000 feet
higher than the highest peaks of the Cascade
Mountains.
When the ice from the last ice age began to
melt, the ocean rose and flooded western
Washington. The flood covered the lowlands.
This left many peninsulas and islands. The two
largest peninsulas in western Washington are the
Olympic and Kitsap peninsulas. Islands also dot the
waterways of western Washington. The San Juans,
Bainbridge, Vashon, and Whidbey are some of the
many popular islands in this region.
Climate
There are two climates within the western
Washington region. They are the west coast marine
and the highland climates. The dominant climate of
the lowlands is west coast marine.
This climate has frequent rainfall throughout
most of the year. Rainfall usually declines during
the summer. Summer temperatures are mild with
limited humidity. Winter temperatures remain
unusually mild given our northern latitude. This is
because of our location next to the Pacific Ocean.
The ocean affects our climate by keeping the
temperature more constant.
In contrast, the mountains of western
Washington have a highland climate. These areas
of western Washington have short, cool, and rainy
summers. The winters are long, cold, and receive
much more snowfall than the lowlands.
The moderate temperatures and abundant
moisture in western Washington support dense
vegetation. Evergreen forests and deciduous trees
cover the landscape like a thick, green carpet. The
highest mountain peaks have little or no vegetation
growing on their slopes. In contrast, the lowlands
have roads, farms, and cities carved from the orest.
As the region has grown, people have removed
more of our forests.
Vegetation
A mild and wet climate allows dense stands
of vegetation to grow in western Washington. The
thick canopy of evergreen trees provides shade for
the plants on the forest floor. Hemlock, cedar,
spruce, alder, and maple trees provide habitats for
animals and other plants in our forests. Without a
doubt, the vegetation in western Washington is very
unique!
The abundant moisture and the shade of
the canopy allow only certain types of plants to
grow. Rhododendrons, azaleas, ferns, and mosses
all grow well in this climate. Mushrooms also thrive
in the shaded environment. Some of the finest
mushrooms in the world grow on our forest floors.
Before you ever pick or eat a mushroom, make
sure it is not poisonous.
Other areas of the forest have been cleared
by logging or fire. Alder, ash, and maple trees grow
well in the forest clearings. River valleys where
sunlight is common also make good homes for
these trees. The river valleys and flood plains are
great locations for farms. Farmers can grow
everything from flower bulbs to cranberries.
Subregions
Western Washington may be divided into
three subregions. Each subregion has its own
unique 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, and
even a rain forest are found here. This area has a
very 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 this
region’s most notable mountains. These rugged
mountains rise nearly 8,000 feet above the Pacific.
Glaciers can be found on the higher peaks. The
mountainous terrain is also home to many alpine
lakes. The rugged terrain makes these small lakes
difficult to access.
Precipitation and melting snow provide
water for many short rivers. They flow into the
Pacific and its many bays and harbors. Willapa Bay
and Grays Harbor are just two of the largest in the
subregion. The largest river in Washington, the
Columbia, forms the southern boundary of the
coastal subregion.
Climate
The coastal subregion has only two
climates. These climates are the west coast marine
and the highland climates. The higher elevations in
the Olympic Mountains have a highland climate.
Rain and snow fall much of the year. In some of the
higher, shaded elevations, glaciers slowly move
down the steep mountain slopes.
The lower elevations of the coastal
subregion are subjected to the west coast marine
climate.The abundant moisture and mild
temperatures are perfect for the dense vegetation
that grows here. In fact, the only temperate rain
forest in the lower 48 states is located here! The
Hoh rain forest is a beautiful place to visit. There
you can see trees more than 500 years old.
Vegetation
Dense stands of trees cover much of this
coastal subregion. Hemlock, cedar, and spruce
provide a thick evergreen canopy. This canopy
allows little sunlight to reach the forest floor. Moss,
ferns, nettles, lupines, lichens, rhododendrons, and
thousands of other plants thrive 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 to
bathe the forest floor where they once stood. The
light and nutrients from the decomposing wood
allow a variety of new plants to thrive in the vacant
area. The seedlings of the cedar and spruce grow
quickly reaching for the light with the 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 spruce
trees 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 that thrived in
this region for centuries.
New plants and vegetation eventually
replaced the natural forest. Alder trees, which once
lived only along the beaches, spread inland.
Raspberries and blackberries, in a bath of light,
spread in every direction. Eventually the loggers
realized that the hemlock was valuable not for its
wood, but instead for its sap. The large giants’ sap
provides rayon for plastics. Hemlocks, the last trees
remaining, were cut as fast as the other trees 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 in our
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
due to the erosion from glaciers and water. Its most
important physical feature is Puget Sound. This
waterway extends south from Everett to Olympia.
Puget Sound, Hood Canal, and the Strait of Juan
de Fuca form the major inland waterways of
western Washington.
Long ago, as the glaciers melted and
retreated north, rising sea level flooded the interior
lowlands of western Washington. The water
covered all the land except only the highest
portions 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 protected waterways
provide excellent ports and shipping lanes. Oceangoing vessels can travel into the lowland region and
safely off-load their cargo.
Rivers and streams also flow from the
nearby Cascade and Olympics mountains into the
lowlands. From the Columbia in the south to the
Nooksack north of Bellingham, there are hundreds
of rivers in this region. These rivers are fed by
heavy rainfall and melted snow. They frequently
flood and deposit their fertile silt on the floodplains.
Climate
The western lowlands has only one type of
climate, the west coast marine. This subregion
receives plenty of rainfall and an occasional
snowfall each year. Most areas receive 40 to 60
inches of precipitation each year.
The Pacific Ocean maintains the mild
temperatures. They tend to be mild throughout the
year. Summers are very comfortable because of
the mild temperatures and infrequent rain.
Temperatures occasionally reach the upper 80s
and 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 the winter
months and early spring. Temperatures are
comfortable because of the influence of the Pacific.
Winter temperatures are rarely extreme, or below
zero, for long periods. An occasional storm, blowing
in from the north Pacific, may bring snow and
subfreezing temperatures to the lowlands. When
these storms hit, they rarely last more than three to
five days.
Vegetation
The natural vegetation in the western
lowlands is mainly made up of conifer and
deciduous forests. These thick forests are different
from those of the coast. The conifers in this region,
in contrast, are smaller than their cousins in the
Olympics. Douglas fir, western red cedar, western
hemlock, and Sitka spruce all grow in the western
lowlands subregion.
Deciduous trees also grow well in the mild
and wet climate. Alder, maple, and oak trees line
the banks of the rivers and grow around the flood
plains. Other plants and shrubs grow quite well in
the forest. Rhododendrons, lupine, azaleas, ferns,
and berries are common in the lowlands. However,
human activity has greatly changed the natural
vegetation. People have cleared the forests for
roads, communities, and factories. Domesticated
plants and trees have replaced some of the original
vegetation of the lowlands.
Western Cascades Subregion
The Cascade subregion of western
Washington is located west of the Cascade
Mountain 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 rugged north
Cascades. Mount Baker is the only major volcanic
peak in this area. However, the North Cascades
have hundreds of jagged granite spires jutting
skyward.
As you travel south through the subregion,
the mountains become less dominant in height but
are still very beautiful. Volcanic peaks now
dominate the mountain skyline. Two major
volcanoes, 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 alpine lakes,
streams, and rivers. The water flowing into them
once fell as either rain or snow. The melting snow
and running rain water collect in the valleys and
continues its journey to the ocean.
Climate
The western slope of the Cascade
Mountains has a highland climate above 3,000 feet.
The lower 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.
Vegetation
Evergreen forests blanket the western
slopes of the western Cascade subregion. The
higher elevations are usually void of trees. Only
shrubs, low lying plants, and mosses can survive
the cooler temperatures and heavy snows. The
warmth of late spring and early summer brings a
variety of alpine flowers and grasses into bloom.
The area above where trees can grow is known as
the tree line. You can see the natural tree line on
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 Cascade Mountain
crest to the Idaho and Oregon borders. The region
of eastern Washington is very different from 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 the rainshadow effect.
Please review page 29 if you would like to learn
more about this climatic feature.
Physical Features
Many unique physical features are found
within the eastern Washington region. These
features include the eastern Cascades, the
Okanogan Highlands, the Rockies, and the Blue
Mountains. The rolling hills of the Palouse and the
Columbia Plateau are other impressive landforms.
Fire and ice helped to form these physical features.
Although the climate is very dry throughout the
year, the region has several major rivers and lakes.
Lake Chelan, Moses Lake, the Potholes, and
Franklin D. Roosevelt Lake are large and popular
freshwater lakes. There are also many alpine 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. It
towers above the North Cascades in eastern
Washington. Mount Adams in southern Washington
is the last of the major volcanic peaks in our state.
The winter snow melt of the Cascade,
Rocky,and Blue mountains fills the many rivers in
the region. The Columbia River is the main river
that flows through eastern Washington. The
Columbia starts its journey to the Pacific Ocean in
British Columbia, Canada. Every other major river
in eastern Washington is a tributary of the
Columbia. A tributary is a river that flows into a
larger river before reaching the ocean. The
tributaries also carve the region’s numerous river
valleys.
Climate
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 severely
reduce the amount of moisture the region receives.
The eastern slope of the Cascades receives no
more than 15 to 30 inches of moisture each year. It
continues to decline the farther east you travel until
you reach the foothills of the Rocky Mountains.
The Columbia Plateau receives less than 15
inches of precipitation a year. Areas which receive
less than 15 inches of precipitation are classified
as semiarid climates. This climate receives most of
their moisture during the winter months. Semiarid
climates receive a little more rainfall than a desert.
Winters are long and frequently very cold. Summer
temperatures, in contrast, are quite hot and dry with
daytime highs reaching 90 to 100 degrees in July
and August. Similar to deserts around the world,
nighttime temperatures drop 30 to 40 degrees from
the daytime high.
The highland climate is found in the higher
mountain elevations. The highland climate has a
very short, cool summer. Summer temperatures
are mild with very little moisture. In contrast, winters
are long and very cold. Daily high temperatures
rarely reach zero. These cold temperatures bring
plenty of snow. The first snow usually falls as the
leaves begin to change color in the higher
elevations. Snow remains throughout the winter.
Melting of the snow begins as spring approaches.
Vegetation
The dry climate allows only certain types of
hardy plants to grow. The semiarid areas have
different types of vegetation than the mountains.
The mountains have widely spaced trees. The
common types are pine and fir. The higher summer
temperatures and lack of moisture force the
evergreens to grow farther apart. They do this to
insure that each tree receives enough moisture to
survive. Ponderosa pine, Douglas fir, and western
larch are the evergreen trees of eastern
Washington. Spread among the evergreen trees
are numerous types of grasses and other
vegetation. The plants that grow in this climate
need to be drought resistant. Traveling down the
slopes of the mountains, moisture decreases.
The trees give way to only grasses and sagebrush.
There is not enough moisture to allow trees to
survive, except next to rivers and streams. Trees
that grow well in these areas are alder, maple, ash,
oak, and elm. These trees are very common along
our streambeds and major rivers. Heading away
from the rivers into the dry and harsh Columbia
Basin, only sagebrush and grasses grow.
journey. These fast-flowing cold rivers have eroded
deep valleys along the mountain slopes. The
Yakima, Kittitas, and Wenatchee valleys are
the largest in the region.
Subregions
Vegetation
The eastern Washington region includes
five subregions. They are the eastern Cascades,
the Columbia Basin, the Okanogan Highlands,
Palouse Hills, and Blue Mountains. These
subregions are both unique and very different
from one another.
The Cascade crest is not only the top of the
Cascades, but it is the point where the vegetation
changes on either side of the crest. Heading east,
the dense forests give way to the Douglas fir and
a variety of pines. Both types of trees do well in the
drier climate to the east. The once dense
undergrowth of vegetation near the crest quickly
changes to mostly sagebrush and grasses.
The northern areas of the eastern Cascades
subregion remain forested with stands of western
larch and Douglas and silver fir. Heading farther
east from the crest, the vegetation continues to
change as trees become fewer and fewer. Finally,
the only trees remaining are the ones growing
along the banks of rivers. Grasses and sagebrush
have replaced the stands of Douglas fir and
ponderosa pine.
Eastern Cascades Subregions
The eastern Cascades subregion includes
all areas east of the crest of the Cascade
Mountains to the Columbia River. This area also
includes the North Cascades and continues east to
the Okanogan River. It is a beautiful and diverse.
Physical Features
Lying within the eastern Cascades
subregion is a very mountainous region. Tall
granite spires jut from the Cascades, such as
Mount Stuart and the Enchantments. Mount Stuart,
at an elevation of 9,470 feet, is one of the highest
non-volcanic peaks in Washington. Southern
mountain peaks are quite different from their
northern cousins in this subregion. The mountains
change from the jagged granite peaks in the north
to rounded basalt mountains and towering volcanic
peaks to the south.
Mount Adams, a volcanic peak, is the
highest mountain in this region. It stands at an
elevation of 12,307 feet. Mount Adams is a unique
volcano. It is composed of at least three volcanic
cones that have merged. Another volcano in this
subregion, and often the least known, is Glacier
Peak. At an elevation of 10,436 feet, this peak is
well hidden by the surrounding peaks of the
Cascade Mountains.
Several rivers flow east from the Cascade
crest to join the Columbia River along its southern
Climate
The rainshadow effect influences the
climate east of the Cascades. Precipitation
amounts decline rapidly from the crest of the
Cascades toward the Columbia River. Moisture
continues to decline even more heading into the
semiarid Columbia Plateau. Total precipitation
drops from 100 inches at the crest to six to eight
inches near the Columbia River. Much of the
precipitation falls in the form of snow during the
long, cold winters.
Columbia Basin Subregion
The Columbia Basin subregion is the driest
area of our state. Scarce fresh water and a lack of
protection from the heat makes it difficult for
vegetation to grow. The Columbia Basin occupies
a small portion of the entire Columbia Plateau.
This region extends east from the Columbia
River to the subregion of the Palouse Hills. It
continues north to the Columbia River and the
Okanogan Highlands. This is a very harsh
environment.
Physical Features
The land in this subregion is mainly flat.
Ravines and channels cut into the terrain. The
Columbia, Snake, and Spokane rivers flow along
the edges of the region. These three rivers have
cut deep valleys into the basalt forming a plateau.
Plateaus are the only major physical feature of the
Columbia Basin subregion. Included are the
Waterville and Columbia plateaus. The Columbia
Basin and the Channeled Scablands have been
severely eroded by water and wind.
Glacial floods cut deep scars called coulees
into the layers of basalt. The coulees may be
hundreds of feet lower than the surrounding basalt
cliffs.
are warm with little precipitation after May and
June. An occasional thunderstorm might rumble
through the region in mid-summer. These storms
bring the threat of lightning and wild fires. Forest
fires are common in the mountains of our state. The
most severe fire season in recent years occurred in
the summer of 1994. Tens of thousands of acres of
forest were burned.
Climate
The climate of the Columbia Basin
subregion is semiarid. The amount of precipitation
varies from five inches to no more than 25 inches
near the foothills of the Rockies. It can get very hot
and dry during the summer. Winter, in contrast,
is very cold and often has drifting snow.
Vegetation
Sagebrush is common and trees are rare,
except along the occasional river bank. Steppe
grasses and sagebrush cover the landscape as far
as the eye can see. Only when the landscape
reaches the foothills of the Rockies are there trees.
Trees and a variety of plants thrive because of the
increased moisture falling on the foothills.
Okanogan Highlands Region
The Okanogan Highlands form the
northernmost subregion in eastern Washington.
This area extends east of the Cascades across the
northeastern portion of the state. The Columbia
and Spokane rivers form the southern boundary
of this subregion.
Physical Features
The terrain of the Okanogan Highlands
subregion is very rugged and mountainous. It
includes the Okanogan Highlands, San Poil and
Selkirk mountains, and a small portion of the
Rockies. These mountains are some of the
youngest granite features in our state. One of
these, the Golden Horn Batholith, includes
several peaks over 8,500 feet.
The Columbia River divides this subregion
into two parts. The western portion includes the
Methow, Okanogan, and San Poil rivers. The
eastern portion includes the Pend Oreille, Colville,
and Spokane rivers. These rivers cut deep valleys
into the mountains and provide a large portion of
the water for the Columbia.
Climate
The Okanogan Highland subregion has very
cold winters and warm summers. The higher
elevations have a highland climate, and lower
elevations are semiarid. Snow falls frequently
during the cold and windy winters. Summers
Vegetation
The Okanogan Highlands subregion is
forested with a variety of evergreen and deciduous
trees. The undergrowth consists of brush and
grasses among the open trees. Fall is a beautiful
time in the region. The steep slopes of the river
valleys are covered with western larch, alder, ash,
and maple trees. They turn brilliant colors as the
autumn frost arrives.
Palouse Hills Region
The Palouse Hills and Blue Mountains form
another subregion in southeastern Washington.
The Palouse Hills extend south from the Spokane
River to the Blue Mountains. The Blue Mountains
extend from northeastern Oregon into the extreme
southeast corner of Washington.
Physical Features
The rugged Blue Mountains and the dune
shaped Palouse Hills are the major physical
features in this subregion. Oregon Butte, the
highest peak in the Blue Mountains of Washington,
rises 6,401 feet. The mountains of this region are
believed to be one source of the basalt floods. The
dikes and fissures here flooded the plateau millions
of years ago.
The largest river of the region, the Snake,
divides the Palouse Hills from the Blue Mountains.
The Touchet, Walla Walla, Grand Rhonde, and
Tucannon rivers also cut deep gorges through this
subregion on their way into the Snake or Columbia
rivers.
Climate
Much of this Palouse Hills subregion has a
modified semiarid climate. It is considered to be
modified because the area receives more
precipitation than other areas of eastern
Washington. The higher elevations of the Blue
Mountains have a highland climate. Snow falls in
this region during most of the winter. Winter tends
to be very cold and windy. Summer, in contrast,
tends to be very hot and dry with little or no
moisture after April.
Vegetation
Steppe grasses and sagebrush cover most
of the subregion. The grasses continue into the
higher elevations along with ponderosa pine and fir
trees. The trees only grow on the moist upper
slopes of the Blue Mountains.
Chapter Summary
The Cascade Mountains separate
Washington into two very different regions. The
climates are as different as black and white.
Within each region are many different subregions
with their own unique climates and vegetation.
The physical features of western and eastern
Washington are also extremely varied. It seems
that the only similarity is that the Columbia
Revegetation and dense forests dominate the west.
In the east, vegetation and trees are few and far
between. Mountains, hills, and plateaus dominate
our landscape.
With such contrasting features, it is
sometimes hard to believe that eastern and
western Washington are part of the same
beautiful state!