Oregon, USA · The Beaver State
weather across oregon — the state where the pacific meets the cascades.
Oregon is divided in two by the Cascade Range — the western Pacific marine zone (Portland, Eugene, the Willamette Valley) and the eastern semi-arid high desert zone (Bend, Pendleton, the Eastern Oregon plateau). The Pacific coast at Astoria experiences some of the heaviest rainfall in the lower 48; the eastern Oregon high desert averages just 10 inches of annual precipitation. The Cascade rain shadow produces one of the most dramatic single-state climate splits in the country.
What is the weather like in Oregon?
Oregon has two distinct climate regions divided by the Cascade Range. Western Oregon (Portland, Eugene) has a Pacific marine climate with cool wet winters and dry summers from late June through mid-September. Eastern Oregon (Bend, Pendleton) has a semi-arid continental climate in the Cascade rain shadow with hot dry summers and cold winters. The Cascades themselves capture Pacific moisture in some of the heaviest snowfall totals in the lower 48.
The seasons, honestly
seasons in oregon.
Oregon seasons run on a Pacific schedule. The wet season runs October through April when Pacific frontal systems cross the state and dump the bulk of the year’s precipitation — most of it on the windward (western) slopes of the Coast Range and the Cascades. Western Oregon experiences persistent stratiform precipitation rather than heavy convective downpours; eastern Oregon sees little rainfall regardless of season.
The dry season runs late June through mid-September when the Pacific subtropical high parks offshore and blocks all weather systems, producing one of the most reliable dry summer climates in the world for Portland, Eugene, and the entire Willamette Valley. Average July high in Portland is 81°F with low humidity and clear skies. Eastern Oregon experiences hotter summers with sustained 95°F+ stretches in the high desert.
Fall (September–October) is the hidden season — clear skies, mild temperatures, and the cleanest air the year produces before the rain returns. Winter (November–March) is mild on the Pacific coast but real continental winter in the eastern Oregon highlands and the central Cascades, with the Mt. Hood and Mt. Bachelor ski areas operating on heavy Pacific orographic snow.
Defining weather events
what the sky does in oregon.
Oregon weather is defined by the Cascade Range. The mountains run north-south through the middle of the state and produce dramatic orographic lift on Pacific air masses, dumping the bulk of the annual precipitation on the windward slopes. Mt. Hood receives over 150 inches of annual snowfall at the higher elevations; the Cascade crest produces some of the heaviest precipitation in the lower 48.
The rain shadow effect on the eastern (lee) side of the Cascades produces the second defining mechanism: the semi-arid high desert climate that defines eastern Oregon. By the time Pacific air descends the eastern Cascades and reaches Bend, Pendleton, and the Eastern Oregon plateau, it has been wrung nearly dry. Bend averages just 11 inches of annual precipitation; the high desert sees less than 10 in some locations.
The Pacific Ocean produces the third mechanism: the cold coastal water that generates persistent summer fog along the Oregon coast (Astoria experiences some of the most fog-prone summer conditions in the contiguous US) and the heavy winter rainfall that gives the western half of the state its temperate rainforest ecosystems.
Pacific moisture pushed up the western slopes of the Cascades produces some of the heaviest rainfall and snowfall totals in the lower 48. Mt. Hood and Mt. Bachelor receive 150–300+ inches of annual snowfall.
The Oregon coast receives heavy Pacific frontal rainfall through the wet season. Astoria averages over 70 inches of annual rainfall; the Coast Range sees over 100 inches at the highest elevations.
Western Oregon experiences one of the most reliable summer dry windows in the contiguous US. The Pacific anticyclonic high pressure system parks offshore from late June through mid September and blocks all precipitation for 8–10 weeks straight.
East of the Cascades, the air has been wrung dry. Bend averages 11 inches of annual precipitation; the eastern Oregon high desert averages 8–10 — semi-arid steppe in the same state as a temperate rainforest.
Oregon experiences major wildfire seasons across the eastern half of the state. The 2020 Labor Day fires were among the most destructive in modern Oregon history, producing significant impacts in the Willamette Valley from smoke transport.
Best cities, by season
where to be in oregon.
Oregon’s best season is the reliable summer dry window from late June through mid September — one of the most consistently beautiful summer climates in the lower 48.
What other weather apps get wrong
why oregon needs a different forecast.
Generic weather apps treat Oregon as one rainy state. They show "rain likely" for Portland in November and "rain likely" for Bend in November as if both are the same forecast, when Bend has one-tenth the annual rainfall of Portland and a completely different climate.
They miss that the Cascade rain shadow produces dramatic east-west climate variation, that the Pacific anticyclonic dry window from late June through mid September is one of the most reliable summer climates in the lower 48, and that Mt. Hood and Mt. Bachelor receive snowfall comparable to the Cascades north of Seattle. AccuWeather treats Astoria and Pendleton as the same forecast despite very different geography.
The Vesper Brief reads Oregon as the bisected state it actually is — Pacific marine western valley, semi-arid eastern high desert — and writes the Cascade orographic lift and the rain shadow as the meteorological events they actually are.
Unlike the Weather Channel, Vesper writes for the part of Oregon you actually stand in.
Frequently asked
about oregon weather.
Frequently Asked Questions
Why is eastern Oregon so much drier than western Oregon?
The Cascade Range divides Oregon into two completely different climates. Pacific air masses moving inland are forced upward over the Cascades, where they cool and dump most of their moisture on the windward slopes. By the time the air descends the eastern Cascades and reaches Bend, it has lost most of its water content — Bend averages just 11 inches of annual rainfall versus Portland’s 36. The same dry air also produces hotter summers and colder winters than the marine-moderated west side.
Does Portland really rain all the time?
No — Portland has one of the most reliable summer dry windows in the United States. Late June through mid September averages fewer than 10 rainy days. The reputation for constant rain comes from the wet season (October–April), when the city averages 155 wet days per year, but most of those days produce light drizzle from low cloud decks, not heavy rain. Total annual rainfall (36 inches) is actually less than New York City (49 inches) — the difference is the distribution.
How much snow does Mt. Hood get?
Mt. Hood receives 150–300+ inches of annual snowfall depending on elevation and aspect. Timberline Lodge at 6,000 feet averages over 250 inches per year and is one of the few US ski areas that operates year-round (with summer skiing on the upper mountain). The combination of Pacific moisture and the Cascade orographic lift produces some of the most reliable mountain snowfall in the West.
When is wildfire smoke season in Oregon?
Wildfire smoke season in Oregon runs from July through early October, with peak smoke events typically in August and September. The eastern Oregon forests, the southern Cascades, and the regional fire complexes all produce smoke that can settle into the Willamette Valley for weeks at a time during major fire years. The 2020 Labor Day fires were among the most destructive in modern Oregon history.
How fog-prone is the Oregon coast in summer?
The Oregon coast experiences some of the most fog-prone summer conditions in the contiguous United States. The cold California Current offshore (in the 50s°F through summer) produces persistent advection fog when warm air crosses the coastline. Astoria, Cannon Beach, and the entire Oregon coast can see fog persist for days at a time during stable summer weather patterns.
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