September in Seattle: Climate & Travel
“Mild and bright — an underrated time to visit.”
Roughly 9 rainy days across the month, on average.
The clocks tick into September and Seattle leans into a mild bite that eases as the sun climbs; you feel it first around the Fremont troll. Averages sit around 21.2°C (70.2°F) by day and 12.9°C (55.2°F) after dark, with rainfall near 57 mm across roughly 8.3 rainy days — settling into steady stretches with clearing between. Daylight runs about 9.3 hours per day, a good working length of light, and the season stamps its signature on details like the cedar canopy of Discovery Park.
The numbers translate to comfortable outdoor pacing. Time around the Fremont troll works well through the middle of the day, and shoulder-hour walks near the Chihuly Garden and Glass land in that specific window where light is generous and heat is not the story. Restaurants keep their outdoor tables in play through the evening.
Reading across 11 complete years (2015–2025), September in Seattle has trended more variable in recent seasons, with the last few years pushing daytime highs and rainfall patterns modestly away from the older normals. The 2026 signal so far tracks the recent shape rather than the long-run midpoint — meaning what you see above is weighted to how this month has actually been running, not a smoothed 30-year picture that masks the shift.
For travellers planning around 2026, this profile is the honest baseline. Match the packing list to the numbers — not to the month name — and you avoid the classic mismatch of arriving with the wrong shell, the wrong shoes, or the wrong daylight assumptions. The rest of this page breaks down what to wear, what to do, and how the season tends to run for Seattle visitors in 2026.
The Freeze is real — locals will smile at you at Trader Joe's and never invite you anywhere. The correct coffee order is a 'cortado' at Milstead or Elm, not a Starbucks anything. Ballard is where Norwegians settled and where the salmon locks let you watch chinook climb concrete steps every August. Never open an umbrella; it marks you as tourist. Locals wear Gore-Tex hoods and consider anything under a half-inch per hour to be 'not really raining.'
What to pack for Seattle in September
With highs around 21.2°C and lows near 12.9°C, layering does the heavy lifting — a single jacket rarely covers a full day.
- a waterproof jacket
- a jumper
- waterproof shoes
- an umbrella
- a beanie
What to pack for Seattle in September
- →Breathable travel pantsAmazon · shop this
- →Compact travel umbrellaAmazon · shop this
- →Reef-safe sunscreen SPF 50Amazon · shop this
- →Polarized sunglassesAmazon · shop this
- →Universal travel adapterAmazon · shop this
- →Compression packing cubesAmazon · shop this
We may earn a small commission on any purchase — it doesn't change the price you pay.
Where to stay in Seattle
We don't review individual hotels — plenty of people do that well. What we do is send you to compare rooms in Seattle across trusted platforms.
Compare hotels on Booking.com→Estimated September trip to Seattle
Shoulder-season pricing — a balance of price and conditions. Rule-based estimates from a couple based in London — actual prices vary.
We may earn a commission if you book through these links, at no cost to you. Estimates use rule-based averages; check partner sites for live pricing.
Plan your Seattle trip
Handpicked services from partners we trust. One tab for everything you'll need after the flight is booked.
Compare rooms in Seattle on Booking.com.
Skip-the-line tickets, day trips, food walks and guided tours.
Compare fares with cashback on every booking.
Instant data on arrival — no roaming charges, no SIM swap.
Flexible monthly coverage for trips of any length.
Compare 900+ rental brands with free cancellation.
Book a driver in advance — fixed price, no queue.
We may earn a commission if you book through these links, at no cost to you.
Things worth doing
Best-fit activities include brewery visits, mountain-view drives, waterfront walks, and market wanders — a mix suited to the month's daylight and weather pattern.
September vs. the rest of the year
How this month compares in Seattle. Tap any month to read more.
highlighted months are among the best time to visit.
Best time to visit Seattle
While September has its own character in Seattle, the data-backed best months to visit Seattle are May, June, July, August. These months combine the most favourable temperatures, rainfall, and sunshine across an 11-year climate record (2015–2025).
See the full best-time-to-visit guide for SeattleOther places with a similar climate right now
Seattle in September — FAQ
Q01Is September a good month for Seattle?
Is September a good month for Seattle?
Yes — this is one of the best months of the year to visit. In September, Seattle averages a high of 21°C (70°F) and a low of 13°C (55°F), with 59mm of rainfall across roughly 9 rainy days. July through mid-September is the 'dry season' when Rainier finally shows itself daily and the Bumbershoot festival takes over Seattle Center.
Q02How warm does Seattle get in September?
How warm does Seattle get in September?
The average high temperature in Seattle during September is 21°C (70°F), with an average low of 13°C (55°F). These figures are averaged from 11 complete years of daily records (2015–2025, Open-Meteo Archive).
Q03Does it rain a lot in Seattle in September?
Does it rain a lot in Seattle in September?
Seattle averages approximately 9 rainy days in September, with a total monthly rainfall of about 59mm. This is based on daily precipitation records where days with 1mm or more of rain are counted as rainy days.
Q04What clothes should I bring to Seattle in September?
What clothes should I bring to Seattle in September?
For Seattle in September, pack layered clothing for changing temperatures, sunscreen and sunglasses, comfortable walking shoes. These recommendations are based on 11 complete years of weather averages for this specific month. Waterproof shoes with aggressive tread — moss-covered brick sidewalks in Pioneer Square become skating rinks in November.
Q05Are there many tourists in Seattle in September?
Are there many tourists in Seattle in September?
Tourist crowds in Seattle during September are typically moderate — shoulder season, a sweet spot between crowds and weather. Consider this when planning accommodation — prices track crowd levels closely. The Freeze is real — locals will smile at you at Trader Joe's and never invite you anywhere. The correct coffee order is a 'cortado' at Milstead or Elm, not a Starbucks anything. Ballard is where Norwegians settled and where the salmon locks let you watch chinook climb concrete steps every August. Never open an umbrella; it marks you as tourist. Locals wear Gore-Tex hoods and consider anything under a half-inch per hour to be 'not really raining.'