The geographic characteristics of the Pacific Northwest define its climate. Together, they determine the ecology of the region, and the flora and fauna it can support.

As a cook, understanding the geography, climate, and ecology of the Pacific Northwest makes it a lot easier to know where to source ingredients, and what ingredients are possible here. The information can also be compared with other parts of the world, to find inspiration and dishes in other cuisines that could be recreated locally.

Geography

Position

The region surrounding Portland ranges from about 40° to 50° latitude. Portland is right in the middle, at 45°. This position is important because daylight patterns are affected by the distance from the equator. The tilt in Earth’s axis is responsible for the change in seasons over the course of the year. The further from the equator, the more extreme the effect. As a result of its latitude, the warm season in the Pacific Northwest is relatively short, which limits some plants’ ability to produce a worthwhile harvest, even though the region’s climate is very mild for how far north it is.

The region is also located on the western side of North America. Due to the direction of Earth’s rotation, the western sides of continents have drier and milder climates than their eastern counterparts.

Finally, the region is located along the Pacific Ocean. Oceans have a moderating effect on temperature extremes. This explains the mild climate found along the coast. Temperature extremes are greater inland where this effect is weaker.

Topography

Like much of the western United States, the topography of the region is highly varied and mountainous. It’s also volcanically active. This volcanic activity is responsible for the region’s fertile soil, which was further enhanced by massive floods at the end of the last Ice Age.

Mountains have a large impact on local climates by blocking prevailing winds, which results in precipitation concentrating on one side of the range and being lower on the other. The area with reduced precipitation is called a rain shadow. In the Pacific Northwest, this effect is especially evident along the Cascade Mountains, which create a rain shadow on the eastern side of the state and concentrate rainfall on the western side, along the coast.

*Major geographic features of the Pacific Northwest.*

Climate

Broadly speaking, the climate of the Pacific Northwest can be divided into two sections, west and east, with the Cascade Mountains as the line of division.

Both sides feature temperate climates with dry summers and wet winters. As you travel south, the climate is warmer and drier. Travel north, it becomes cooler.

The western side has a mild coastal climate with high precipitation. Temperatures are moderated by the Pacific Ocean and there are fewer temperature extremes. The area supports extensive temperate coniferous rainforests.

The eastern, inland side has an arid and continental climate. It is affected by greater temperature extremes and receives less annual precipitation. Much of it falls as snow. Precipitation increases in mountainous areas. The area features deserts, plains, and open conifer forests.

Resources

For a more detailed look at the climate of the Pacific Northwest, it helps to look at a variety of classification systems and maps. I reference some of the below systems and information when discussing ingredients.

Köppen system

The Köppen system was designed in the early 20th century by German-Russian climatologist Wladamir Köppen. The classification system was based in largely on Köppen’s experience as a botanist. It provides insights on ecosystems, and in turn, on what grows in a given region.

Under the Köppen system, climates are divided into five main groups:

tropical (A): warm year-round
arid (B): low precipitation. This group includes steppe and desert climates.

temperate (C): mild winters.
continental (D): cold winters. Continental climates can be considered a subset of temperate climates, but with greater temperature extremes.
polar (E): cold year-round. This group includes tundra and ice-cap climates. Polar climates are also known as alpine climates when they are found at high elevations.

The main groups are then assigned a second letter according to seasonal precipitation patterns and a third letter according to temperature patterns. There are 30 Köppen climate types in total. Of these, 14 of them are found in the Pacific Northwest. We have a highly varied landscape, with many climate types. However, of the 14 that are found here, we have 5 that are especially common:

warm-summer mediterranean (Csb)
hot-summer mediterranean (Csa)
oceanic (Cfb)
steppe (BSk)
continental warm-summer mediterranean (Dsb)

Mediterranean (Csa and Csb)

Mediterranean climates are temperate and characterized by dry summers and wet, mild winters. The overwhelming majority of annual precipitation is received in the cool season (winter and adjacent months). Mediterranean climates are only found in about 2% of the world.

In the Pacific Northwest, the predominant climate type in the Pacific Northwest is warm-summer mediterranean (Csb), which has cooler summers than the hot-summer mediterranean (Csa) climate found in California. The Pacific Northwest is the largest single area in the world that features a mediterranean climate with warm summers.

The cold-summer variant can be found in small amounts at high elevations.

Oceanic (Cfb)

As you move further north into Washington and British Columbia, the climate becomes more oceanic and similar to the western side of Europe. Oceanic climates are characterized by consistent precipitation throughout the year, cool to warm summers and mild winters. Temperatures are also consistent, and stay within a relatively narrow annual temperature range with few extremes.

Many coastal parts of the Pacific Northwest can be considered transition areas between Mediterranean and oceanic climates.

Steppe (BSk)

Inland, the climate changes to a cold semi-arid (BSk) climate, also known as a steppe climate, due to the rain shadow created by the Cascade Mountains, altitude, and the greater distance from the Pacific Ocean. Defining characteristics of the climate are low year-round precipitation and larger temperature variations between night and day. The climate features dry, warm-to-hot summers. Most of the precipitation is received in winter, often in the form of snow.

There are a few cold desert (BWk) areas near the steppe climates. These receive even less precipitation.

Continental mediterranean (Dsb)

The continental mediterannean climate is generally found in mountainous areas near mediterranean climates.

In many ways, this continental climate is just an extension of the mediterranean climate. It exhibits similar precipitation patterns, with most of it received in the cool season, but has greater temperature differences between seasons because the moderating influence of the ocean is weaker. This climate type is rare in the world.

In the Pacific Northwest, we mainly see the warm-summer variant (Dsb).

California

Idaho

Oregon

Washington

Hardiness zones

The USDA hardiness zone system is used in horticulture to determine what plants can be grown in an area. It has its limitations, though, because it’s based only on the average extreme minimum temperatures found in an area over the course of a year and does not take into account other climatic differences. That said, it makes a good starting point for researching plants, since many can be ruled out simply based on their hardiness.

There are 13 hardiness zones under this system, with “a” and “b” subdivisions added for further detail. The Pacific Northwest as a whole ranges from zones 3b to 10a.

Oregon: 4b to 9b
Washington: 4a to 9a
Northern California: 5b to 10a
Idaho: 3b to 7b

Because the USDA hardiness system uses averages, it can paint an inaccurate depiction of the lowest temperatures that may affect an area. In Portland, for example, we are subject to a cycle of extreme low temperatures that occur intermittently. Cold snaps like that don’t affect the average much overall, but they can still kill a plant that would otherwise be OK. With regards to commercial agriculture, no producer will be willing to grow a perennial plant that might get wiped out in a decade.

For the Portland area, I look for perennial plants which can handle about 0°F to 5°F, since these are temperatures which have historically hit the area. Of course, climate change will likely raise these numbers, but as it currently stands, this is a good gauge.

For a more detailed map check out the USDA website.

Precipitation patterns

Overall annual precipitation in the Pacific Northwest is actually lower than might be expected, since the region as a whole is more arid. The distribution of precipitation is very unequal, with some parts of the western side of the Pacific Northwest receiving the highest precipitation levels in the lower 48 states.

Soil pH

One impact of the difference in precipitation between the arid and temperate parts of the Pacific Northwest is expressed in the acidity or alkalinity of the soil (pH balance). The soil is more alkaline in arid climates than the soil in the forested, temperate climates, which can be very acidic due to the leaching of minerals caused by elevated rainfall. Plants have varying soil pH preferences which can affect their success in different regions.

Geography and climate