Geography of the Pacific Northwest
The Pacific Northwest — from Oregon's high desert to the BC Coast Mountains — is one of the most climatically varied regions in North America. Mountains, oceans, and pressure systems conspire to create radically different worlds within a few hours' drive of each other.
West → East: One Transect, Seven Worlds
Drag the scrubber across this cross-section running from the Pacific coast over the Olympic Mountains, through Puget Sound, across the Cascades, and into the high desert. In roughly 400 miles, annual rainfall drops from 140 inches to 7 inches.
Puget Sound Lowlands
0–2,000 ft
Annual Rainfall
36–52"
Temperature Range
40–80°F
Vegetation
Douglas-fir, red alder, urban forest
Protected from the worst Pacific storms by the Olympic rain shadow, the Puget lowlands enjoy a relatively mild maritime climate. Seattle sees about 38 inches of rain annually — less than New York City — though it's spread across many grey days. This is the most densely populated zone in the PNW.
Notable Microseasons Here
The Forces at Work
Toggle the layers below to see what's shaping the weather on any given day — then click a region to discover which microseasons are most vivid there.
Why Geography Makes the Seasons
The Rain Shadow Effect
When Pacific air masses rise over the Olympics and Cascades, they cool and drop their moisture. By the time air descends on the eastern side, it has lost most of its water — creating high-desert conditions within miles of temperate rainforest. This single phenomenon explains more about PNW climate than any other.
The Pacific High
Every summer, a high-pressure system builds offshore, deflecting storm tracks northward and delivering the PNW's characteristic dry summers. When it retreats in September, storms flood back in — beginning a new cycle of the seasonal calendar. The timing of the Pacific High's arrival and departure defines the whole arc of the year.
Marine Influence
The Pacific Ocean acts as a thermal flywheel, keeping coastal temperatures mild year-round. Water holds heat longer than land, moderating the region's winters and cooling its summers. The further inland you travel from the coast, the more continental the climate becomes — winters colder, summers hotter, and swings more extreme.