Washington, USA · The Evergreen State
weather across washington — two states in one, divided by the cascades.
Washington is a meteorological textbook of orographic effects. The Cascade Range runs north-to-south through the middle of the state, dividing it into the Pacific marine west (Seattle, Tacoma, Olympia) and the inland continental east (Spokane, Yakima, the Tri-Cities). The west side is among the wettest places in North America; the east side is semi-arid steppe. The forecast in one half has nothing to do with the forecast in the other.
What is the weather like in Washington?
Washington has two distinct climate regions divided by the Cascade Range. Western Washington (Seattle, Tacoma) has a Pacific marine climate with cool, wet winters and dry summers from late June through mid-September. Eastern Washington (Spokane, the Tri-Cities) has a semi-arid continental climate in the Cascade rain shadow with hot dry summers and cold snowy winters. The Cascades themselves capture Pacific moisture in some of the highest snowfall totals in the lower 48.
The seasons, honestly
seasons in washington.
Washington 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 Cascades. 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 the Seattle metro.
Spring (April–June) is short, dramatic, and welcome on the west side, with the marine layer gradually receding and the warm season just beginning. Fall (September–October) is the hidden season — clear skies, mild temperatures, and the cleanest air the year produces before the rain returns.
Eastern Washington follows a different schedule. The Cascade rain shadow produces a continental climate with four hard seasons — cold winters with snowfall totals around 50 inches in Spokane, hot dry summers with frequent wildfire smoke events, and short transitional spring and fall windows. The Palouse winds tear across the open rolling country between the Cascades and the Rockies, kicking dust visible from satellite during dry months and amplifying wind chill during winter cold air outbreaks.
Defining weather events
what the sky does in washington.
Washington weather is defined by two large-scale mechanisms working at the state’s geographic axis. The Pacific Ocean and the marine layer dominate the western half — the cold California Current upwelling produces the marine air that pushes inland through the Olympics and the Puget Sound, the Olympic rain shadow creates a dry pocket on the eastern side of the Olympic Peninsula, and the Cascade orographic lift produces the heaviest rainfall and snowfall in the lower 48 (Mt. Baker holds the world snowfall record for a single season at 1,140 inches in 1998–99).
East of the Cascades, the rain shadow effect produces a completely different climate. Pacific air that crosses the Cascades has been wrung nearly dry, and what reaches Spokane and Yakima is continental in character — hot dry summers, cold winters, and the wildfire smoke season that arrives every July from fires in eastern Washington, Idaho, Oregon, and British Columbia.
Pacific moisture pushed up the western slopes of the Cascades produces some of the highest rainfall and snowfall totals in the lower 48. Mt. Baker received 1,140 inches of snow in the 1998–99 season, the world record.
East of the Cascades, the air has been wrung dry by the orographic lift. Spokane averages 17 inches of annual rainfall versus Seattle’s 38, and Yakima averages just 8 inches — semi-arid steppe in the same state as a temperate rainforest.
Concentrated Pacific moisture plumes ("pineapple express" storms) produce the heaviest rainfall events of the year, dumping several inches of rain on the Seattle metro and feet of snow in the Cascades in 24 hours.
Wildfires in eastern Washington, Idaho, Oregon, and British Columbia produce smoke that settles into the Spokane and Yakima valleys, producing AQI readings in the unhealthy range for weeks at a time during peak fire years.
Sequim and Port Townsend on the eastern side of the Olympic Peninsula receive only ~16 inches of annual rainfall — about half of Seattle’s and a fifth of what Forks on the western Olympic side receives.
Best cities, by season
where to be in washington.
Washington’s best city depends entirely on which side of the Cascades you visit and which season you came for. The west side (Seattle) shines in summer; the east side (Spokane) shines in spring and fall.
What other weather apps get wrong
why washington needs a different forecast.
Generic weather apps treat Washington as a single rainy state. They show "rain likely" for Seattle in November and "rain likely" for Spokane in November as if both are the same forecast, when Spokane has one-third the annual rainfall of Seattle and a completely different climate.
Apple Weather treats Yakima and Olympia as the same forecast despite the Cascades dividing them into a temperate rainforest west side and a semi-arid steppe east side. AccuWeather’s "feels like" temperature ignores the Cascade rain shadow effect entirely.
The Vesper Brief reads Washington as the bisected continental state it actually is — Pacific marine west, semi-arid east, Cascade alpine in between — and writes each region’s atmosphere as the distinct climate it actually is. Unlike the Weather Channel, Vesper distinguishes between Olympic rain shadow drizzle and Inland Northwest dust haze.
Unlike the Weather Channel, Vesper writes for the part of Washington you actually stand in.
From the journal
writing about washington.
Frequently asked
about washington weather.
Frequently Asked Questions
Why is Seattle’s climate so different from Spokane’s despite being in the same state?
The Cascade Range divides Washington 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 (Seattle averages 38 inches per year). By the time the air descends the eastern Cascades and reaches Spokane it has lost most of its water content — Spokane averages only 17 inches annually. The same dry air also produces hotter summers and colder winters than the marine-moderated west side.
Does it really rain all the time in Seattle?
No. Seattle 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 (38 inches) is actually less than New York City (49 inches) — the difference is the distribution.
What is the Olympic rain shadow?
The Olympic Mountains rise 7,000+ feet on the western edge of the Olympic Peninsula and force Pacific moisture to drop most of its water on the windward (western) side. By the time the air descends the eastern slopes toward Sequim, Port Townsend, and the eastern peninsula, it has been wrung nearly dry. Sequim averages only ~16 inches of annual rainfall — about half of Seattle and a fifth of what Forks on the western side receives. The shadow extends across the Strait of Juan de Fuca to the southern Vancouver Island and the San Juan Islands.
When is the wildfire smoke season in eastern Washington?
Wildfire smoke season in eastern Washington runs from July through early October, with peak smoke events typically in August and September. Smoke arrives from fires in eastern Washington, Idaho, Oregon, and British Columbia, and the inland basin geometry traps it for days at a time. Spokane, Yakima, and the Tri-Cities can see AQI readings in the unhealthy range for weeks during major fire years. The clearest air typically arrives after the first significant fall cold front breaks the smoke pattern.
How much snow does the Cascade Range receive?
The Cascade Range receives some of the highest snowfall totals in the contiguous United States. Mt. Baker holds the world record for single-season snowfall at 1,140 inches (95 feet) during the 1998–99 winter. Mt. Rainier and the high Cascades regularly receive 600+ inches per year. The combination of Pacific moisture availability and the Cascade orographic lift produces the conditions for the world’s deepest mountain snowpack.
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