If you’ve ever looked at a satellite map of the Pacific Northwest during a winter storm, you might have seen something weird. A literal hole in the clouds. While Seattle is getting drenched and the Olympic Rainforest is basically becoming an aquarium, there’s this tiny, sunny circle sitting right over the Dungeness Valley. Locals call it the Blue Hole.
Honestly, it’s the main reason people move here. But if you’re checking a standard weather forecast Sequim Washington on your phone, you might be getting lied to. Most apps just scrape data from regional models that assume Sequim is as wet as Port Angeles or Everett. It’s not.
The Science of the Sequim Rain Shadow
Basically, the Olympic Mountains are a giant wall. When moist air blows in from the Pacific, it hits those peaks and has nowhere to go but up. As it rises, it cools and dumps all its water on the west side (sorry, Forks). By the time that air reaches the leeward side—where Sequim sits—it’s wrung out like an old sponge.
This is called the orographic effect.
Because the air is descending and warming as it moves toward the Strait of Juan de Fuca, it actually evaporates existing clouds. That’s why you can stand in downtown Sequim under a patch of blue sky while watching dark grey curtains of rain fall just five miles away in every direction.
Annual Rainfall Realities
To give you some perspective on how dramatic this is, look at the numbers. They don't make sense until you see them side-by-side.
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- Forks, WA: ~120 inches per year.
- Seattle, WA: ~38 inches per year.
- Port Angeles, WA: ~25 inches per year.
- Sequim, WA: ~16 inches per year.
Yeah, 16 inches. That is roughly the same amount of rain as Los Angeles, California. You’ve got prickly pear cactus growing wild in the Dungeness National Wildlife Refuge just a short drive from a temperate rainforest. It’s a total climate anomaly.
Why Your Weather App is Probably Wrong
Kinda annoying, right? You wake up, check your iPhone weather, and it says "100% chance of rain." You cancel your hiking plans, look out the window an hour later, and it’s blindingly sunny.
Most generic weather forecasts for Sequim Washington use a broad-brush approach. They see a massive low-pressure system moving into Western Washington and just apply a "Rain" icon to the whole map. They don't account for the micro-climate physics of the rain shadow.
If you want the real story, you have to look at the UW WRF-GFS model or local stations like the one at Washington Harbor. These high-resolution models actually factor in the terrain of the Olympics. If the wind is coming from the Southwest, the rain shadow is usually "on." If the wind shifts and comes from the North or East (a " Fraser Valley Outflow"), the shadow breaks, and Sequim gets hit just like everywhere else.
Seasonal Vibes: What to Actually Expect
Don't get it twisted—Sequim isn't Hawaii. It still gets cold, and it still gets grey. The difference is the volume of water and the frequency of "sun breaks."
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Winter (November - February)
This is when the rain shadow works overtime. You’ll have weeks where the ground is damp but it never actually pours. Temperatures usually hover in the 40s. Snow is rare because the mountains block the moisture, but when a cold snap hits and moisture sneaks in from the Strait, you can get a "surprise" foot of snow that shuts the town down for two days.
Spring (March - May)
Spring is arguably the best time for the weather forecast Sequim Washington to be in your favor. While the rest of the state is dealing with "June Gloom" and endless drizzle, Sequim starts drying out early. The fields start greening up, and the Olympic peaks are still covered in white. It's gorgeous.
Summer (June - August)
This is Lavender season. The Sequim Lavender Weekend (usually the third weekend in July) is famous because the weather is almost guaranteed to be perfect. Highs are usually in the low 70s. It rarely gets "hot-hot" because of the marine breeze off the water. If it hits 80 degrees, locals start complaining about the heat wave.
Fall (September - October)
September is the secret best month. The tourists are gone, the air is crisp, and the rain shadow keeps the early autumn storms at bay. You get these deep orange sunsets over the Strait that are honestly hard to beat.
Microclimates: Not All of Sequim is Dry
Here is something most real estate agents won't tell you: the rain shadow has "edges."
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If you live up on Blue Mountain or near the foothills of the Olympics, you're going to get more rain. You’re literally catching the water as it starts to dump. If you live out toward Agnew or near the Dungeness Spit, you’re in the heart of the dry zone.
Even a two-mile difference can mean an extra 5 inches of rain a year. If you're gardening, that's a huge deal. You go from needing a heavy-duty irrigation system to wondering why your tomatoes are drowning.
Actionable Tips for Navigating Sequim Weather
If you're visiting or living here, stop relying on the default weather app on your phone. It’s a recipe for disappointment.
- Watch the Wind Direction: If the forecast says winds are from the SW, pack your sunglasses even if it says rain. If winds are from the North/Northeast, grab the raincoat.
- Use the "Olympic Rain Shadow" Website: There are hobbyist sites that run specific models just for this area. They are much more accurate than big-box weather sites.
- Dress in Layers: The temperature can swing 20 degrees the moment the sun drops behind the peaks or the fog rolls in from the Strait.
- Check the Dungeness Spit Webcam: Want to know if it's actually sunny? Look at the live feed from the Lighthouse. It’s the ultimate "truth-teller" for local conditions.
The weather forecast Sequim Washington is less of a prediction and more of a suggestion. The mountains have the final say. Understanding that "Blue Hole" logic makes the difference between a soggy weekend and a perfect outdoor adventure.
Track the real-time rain shadow movement by checking the North Puget Sound radar specifically for "shadowing" gaps behind the Olympic Mountains before you head out.