Washington State’s weather really changes from month to month. The difference between the rainy western coast and the drier eastern regions can be pretty dramatic. The Cascade Mountains split the state in half, acting like a wall that creates two totally different climate zones.
Washington gets its wettest months from November through February. July and August, on the other hand, bring the warmest and driest weather across the state. In winter, most areas hover between 35-45°F, and the mountains get hammered with snow. During summer, temperatures jump to 60-85°F, and eastern Washington often feels a lot hotter than the coast.
Knowing these monthly weather patterns helps everyone—locals and visitors alike—plan for everything from ski trips in winter to wildflower hikes in spring. Every season has its own perks and challenges, whether you’re slogging through November rain or soaking up the sunshine in July and August.
Overview of Monthly Weather in Washington
Washington state goes through clear seasonal changes. Winters are wet, summers are dry, and the Cascade Range makes sure the west and east sides feel like separate worlds. Temperatures run from winter lows near 35°F to summer highs around 85°F. Rainfall swings wildly, from less than an inch in summer to over 9 inches during the winter months.
Typical Weather Patterns Across the Year
Washington follows a Mediterranean-ish climate, with obvious wet and dry seasons. December through February bring the coldest days, with temperatures sitting between 35-47°F and the most rain—think 5-10 inches each month.
Spring creeps in from March to May. Temperatures rise from 40°F in March to 65°F by May. Rain starts to let up during these months, dropping from 7 inches in March to only 2-4 inches by May.
June through August is Washington’s driest stretch. Temperatures peak at 70-85°F, and rain is almost an afterthought—just 0.5-3 inches a month. July and August usually serve up 20-26 sunny days each.
Fall cools things down and brings the rain back. September stays warm, 60-75°F, but by October, it’s down to 50-65°F. Rainfall climbs from 1-3 inches in September to 3-6 inches in October, and November can hit 5-9 inches.
Comparing Western and Eastern Washington
The Cascade Range splits Washington into two very different climate zones. Western Washington gets a marine climate thanks to the Pacific Ocean, while the east feels a lot more continental.
Western Washington gets way more rain all year. Seattle and the coast usually rack up 6-10 inches of rain in winter, and cloudy skies are pretty much the norm. Temperatures stay moderate because of the ocean, rarely dipping below freezing or above 80°F.
Eastern Washington stays much drier, and the temperature swings are bigger. Summers often hit the mid-80s, almost desert-like at times. Winters get colder, but there’s a lot less precipitation than on the west side.
The mountains create a rain shadow. Most of the Pacific storms dump their moisture on the west, leaving the east side much drier. Annual rainfall in the east is often just half of what the west gets.
Key Weather Conditions to Expect
Winter brings snow to the mountains and rain with overcast skies to lower areas. Western regions slog through 20-25 overcast days each month. Eastern areas stay drier but feel colder.
Summer is all about sunshine, with 15-26 sunny days per month. The coast stays cool, while inland spots heat up. Wildfire risk jumps during these dry months, especially in the east.
Spring and fall are wild cards. Spring brings wildflowers and longer days. Fall delivers beautiful foliage and harvest time in wine country.
Extreme weather isn’t unheard of. Sometimes winter storms dump heavy snow in the mountains. Eastern areas can get hit with heat waves in summer. Ice storms show up now and then in winter, and the coast can get battered by strong winds during storms.
Monthly Weather Breakdown by Region
Washington State’s weather can change a lot from region to region. The Cascade Range splits the state into distinct climate zones. Western areas get mild, rainy winters and dry summers, while the east faces more extreme temperatures and far less rain.
Seattle’s Monthly Climate Trends
Seattle sits in a maritime climate with pretty predictable seasons. December through February means lots of rain and mild temps in the 40s and 50s.
Spring shows up slowly from March to May. Temperatures move from the mid-50s to low 60s, and while rain eases up, it doesn’t exactly disappear.
Summer—June through August—brings the driest stretch. Daytime highs reach the mid-70s to low 80s. Rainfall hits its yearly low.
Fall Weather Pattern:
- September: Warm and dry
- October: Cooler, rain picks up
- November: Cool and wet returns
Seattle averages about 37 inches of rain a year. Most of it falls between October and April. Snow is rare and usually doesn’t stick around.
Eastern Washington Weather Differences
Eastern Washington deals with a continental climate and bigger temperature swings. Winters often drop below freezing, with highs in the 30s and 40s.
The region gets way less rain than the west. Annual totals range from 10 to 20 inches in a lot of spots.
Summer is hot and dry, with temperatures often in the 80s and 90s. Some places even hit over 100°F at the peak.
Temperature Extremes by Season:
- Winter: Lows often below 20°F
- Spring: Quick warm-up from 50s to 70s
- Summer: Highs regularly over 85°F
- Fall: Fast cooldown, frost by October
Snow piles up more often than on the west side. Winter storms can drop several inches that stick around for weeks.
Coastal Versus Inland Variability
Washington’s coastal areas have the most stable temperatures year-round. The ocean keeps winter lows near 40°F and summer highs close to 70°F.
Inland valleys, like the Puget Sound region, see bigger temperature swings. They’re more variable than the coast but not as extreme as eastern Washington.
Elevation matters a lot. Mountain areas get heavy snow from November through March, and some peaks keep their snow into summer.
Precipitation Patterns:
- Coastal areas: 60-100+ inches a year
- Puget Sound region: 35-45 inches
- Eastern valleys: 8-15 inches
Winds can be all over the place. The coast gets strong ocean winds in winter storms. Eastern areas sometimes get gusty winds when weather systems change.
Seasonal Highlights and Extremes
Washington State swings between heavy winter rain in the west and blazing summer heat in the east. The geography here creates some of the wildest weather contrasts in the lower 48.
Winter Temperatures and Precipitation
Western Washington gets pounded with winter rain. Coastal spots often see 6-10 inches each month from November through February.
The Olympic Peninsula is a rain magnet, clocking over 140 inches a year. Some years, certain places get more than 200 inches.
Mountain regions get incredible snowfall. Mount Baker is legendary for snow—over 1,100 inches in a single season, if you can believe it.
Winter temperatures really depend on where you are:
- Coastal areas: 35-45°F, rarely freezing
- Mountain peaks: Often below 0°F
- Eastern valleys: Can hit -20°F or even lower
The Cascades split the state. Seattle gets 37 inches of rain a year, while Spokane only sees about 17.
Summer Heat and Drought Patterns
Eastern Washington turns into a dry, hot landscape in summer. Temperatures regularly top 90°F from June through August.
The Columbia River Valley is famous for extreme heat. Heat waves can push temps up to 110°F. These hot, dry stretches put a lot of drought stress on farms.
Rain almost disappears east of the Cascades. Many spots get less than an inch from July to September.
Western Washington enjoys much milder summers. Seattle rarely breaks 80°F, though the occasional heat dome can push it past 100°F.
The difference is huge. The west stays green and mild, while the east bakes under the sun. Fire danger climbs and sticks around into fall.
Spring and Autumn Transitions
Spring takes its time in Washington. The west starts warming up in March, but the east can still see snow in April.
April and May shake things up. Rain in the west drops from 5 inches to 2 inches a month. Eastern Washington warms up fast after winter.
Autumn comes on quickly. September still feels like summer, with 18-22 sunny days across the state. By October, rain and cooler temps return.
Fall weather flips fast. Western Washington’s rainfall jumps from 3 inches in September to 6 inches in October. The east side sees its wettest months too.
November brings a quick drop in temps. Suddenly, it’s winter.
Best Time to Visit Washington
June through September usually delivers the best weather for visiting Washington State. Peak season means sunshine but also bigger crowds. If you want fewer people, the shoulder seasons can be a sweet spot.
Optimal Months for Travel
June through August is prime time for Washington. Warm temps and dry skies make it the go-to stretch.
July and August bring the best summer weather, with most areas sitting between 60-80°F. Eastern Washington can climb to 85°F. Rain is rare, just 0.5-2 inches a month.
September is still great, with 60-75°F days and light rainfall (1-3 inches). There are usually more sunny days than cloudy ones.
May and early June are solid shoulder season picks. Temperatures rise to 50-70°F, and rainfall is moderate at 2-4 inches. Wildflowers bloom, and hiking trails open up.
November through February can be tough. Rain piles up to 5-10 inches monthly in the west. Temperatures drop to 35-47°F, and skies stay gray most days.
Popular Seasonal Activities
Summer activities peak in July and August. Mount Rainier and North Cascades National Parks offer the best hiking, with high trails finally clear of snow.
The San Juan Islands are perfect for whale watching from June to September. Ferries run often, but places fill up fast.
Wine country is at its best in September during harvest. Yakima Valley and Walla Walla vineyards offer tours, tastings, and great cycling weather.
Seattle’s outdoor spots shine brightest in summer. Pike Place Market, the waterfront, and city parks are all at their best for strolling and sightseeing.
Spring events include April’s Skagit Valley Tulip Festival. Cherry blossoms pop in Seattle parks. The Columbia River Gorge is carpeted with wildflowers.
Avoiding Peak Tourist Crowds
Late May and early June offer good weather and smaller crowds. Hotels cost less than in July or August, and it’s still comfortable at 55-70°F.
September is another sweet spot. The weather holds, but most tourists head home after Labor Day.
Visit on weekdays during summer to dodge the biggest crowds at popular spots. National parks and Seattle attractions calm down from Tuesday to Thursday.
Booking ahead is crucial for July and August. Reserve 3-6 months out for busy places like Olympic National Park or the San Juan Islands.
Winter—December through February—means few crowds, but you’ll need to be flexible with plans. Indoor attractions in Seattle stay open all year.
Factors Influencing Washington’s Monthly Weather
Three main things shape Washington’s wild weather: the Cascade Mountains split the state, the Pacific Ocean keeps the west mild, and the terrain creates tons of local variations.
Cascade Range and Rain Shadow Effect
The Cascade Mountains slice Washington into two climate zones with totally different weather. These peaks block moisture-packed air from the Pacific.
Western Washington takes the brunt of ocean storms. Air masses rise up the western slopes, cool off, and drop rain or snow.
Seattle and Tacoma get 35-40 inches of rain each year. The western slopes can see over 100 inches annually at higher spots.
Eastern Washington sits in the rain shadow. Air flows down the eastern slopes, warms up, and dries out.
Spokane only gets about 17 inches of rain per year. The Yakima Valley gets even less, around 8-10 inches.
Temperature swings are just as big. The east side deals with hotter summers and colder winters, thanks to its continental climate.
Pacific Ocean’s Impact
The Pacific Ocean basically acts as a massive temperature buffer for western Washington all year. Ocean water changes temperature pretty slowly compared to land.
Summer cooling kicks in when marine air pushes inland. Even in July and August, the coast almost never sees temperatures above 80°F. Seattle usually tops out at 76°F in July.
Winter warming sets in as the ocean gives off stored heat. You won’t find many freezing nights near the coast. It’s rare for snow to stick in Seattle, especially compared to spots farther inland.
Storms rolling in from the ocean drop most of western Washington’s rain between October and April. Sometimes these systems dump several inches of rain in just a day.
Marine layer pops up when chilly ocean air runs into warmer land. That’s why you see those morning clouds and fog, but usually, the sun burns them off by afternoon.
The ocean’s grip on the weather fades the farther you get from shore. Head 50 miles inland and you’ll notice way more swings in temperature than you do right on the coast.
Microclimates within the State
Washington has dozens of distinct microclimates thanks to its mountains, valleys, and quirky geography. You can drive just a few miles and suddenly the weather feels totally different.
Mountain elevations make the temperature drop about 3-4°F for every 1,000 feet you climb. Mount Rainier keeps its snowcap all year, but the valleys nearby get to enjoy pretty mild summers.
River valleys steer weather systems and cook up their own conditions. The Columbia River Gorge, for example, funnels wild winds that can hit over 50 mph during winter storms.
Urban heat islands form in cities like Seattle and Spokane. All that concrete and asphalt soaks up heat during the day. Downtown stays 5-10°F warmer than the suburbs after dark.
Puget Sound helps keep temperatures steady for nearby towns. Living near the water means less frost and more stable weather than neighborhoods just a few miles inland.
The Olympic Peninsula makes its own weather, too. The west side gets some of the heaviest rainfall anywhere in the continental U.S.
Planning Tips Based on Monthly Weather
Washington’s weather is all over the map, so you’ll want to plan ahead for gear and safety. The difference between the misty western forests and the dry eastern side can really catch you off guard.
Packing Recommendations
Winter months (December-February) call for layers. Bring waterproof jackets, warm base layers, and insulated boots if you’re headed to western Washington.
Temperatures usually land between 35 and 47°F, and rain can pile up to 6-10 inches each month. If you’re going east, you’ll need even more cold-weather gear since it’s drier but colder.
Spring months (March-May) are unpredictable, so pack for anything. Light rain jackets, breathable layers, and comfy walking shoes should cover you.
- March: Definitely bring a waterproof jacket
- April: Light layers work for 45-58°F
- May: You can probably leave some rain gear at home
Summer months (June-August) usually mean you can skip the rain gear. Go for lightweight clothes, sunscreen, and hiking boots if you’re planning to be outside.
Eastern Washington heats up to about 85°F, while the coast hangs around 70°F. With 20-26 sunny days a month, sunscreen isn’t optional.
Fall months (September-November) are all about transition. You’ll want rain gear, warm layers, and waterproof shoes as things start shifting toward winter.
Outdoor Safety and Preparation
You really need to keep an eye on the weather all year in Washington state. In winter, check the forecast every day—conditions can flip fast.
Mountains bring their own set of challenges. From December through March, snow piles up quickly, so you’ll want to know about avalanches and have the right gear.
When heavy rain hits the western regions, flash floods can happen out of nowhere. If November drops 5-9 inches of rain, it’s best to steer clear of low spots and creek beds.
Summer in eastern Washington can get surprisingly hot. Bring extra water, and maybe stick to the cooler mornings if it’s over 80°F.
Up in the mountains, hypothermia isn’t just a winter thing. Even on summer hikes, it makes sense to pack a warm layer and some kind of emergency shelter.
Rivers and lakes change with the seasons. Spring snowmelt turns the water wild, but summer usually brings safer conditions for getting out on the water.