Seattle weather in September
“Mild and bright — an underrated time to visit.”
Roughly 9 rainy days across the month, on average.
September is one of Seattle's finest months. Daytime temperatures average 21.3°C (70°F), while nights cool to 12.9°C (55°F). You'll see roughly 60mm of rainfall spread across about 9 days, so rain is present but not overwhelming. With 9.3 hours of sunshine daily, you get plenty of light for exploring the city's neighborhoods, waterfront, and nearby mountains.
This is peak season for outdoor festivals and events. The summer crowds thin out slightly, making September ideal for visiting Pike Place Market, hiking around Mount Rainier, or catching live music venues without peak-season chaos. The city has a relaxed, energetic vibe as locals and visitors enjoy warm, dry stretches between occasional rain showers.
For 2026, pack layers and a light rain jacket—Seattle's weather can shift throughout the day. September is an excellent time to visit before autumn settles in, offering comfortable temperatures and fewer tourists than summer while maintaining plenty of daylight.
What to pack for Seattle in September
Layer up for Seattle's variable September weather. Mornings and evenings are cool, but afternoons warm up nicely. A light rain jacket is essential, along with breathable base layers and a comfortable sweater you can tie around your waist.
- Lightweight rain jacket (water-resistant shell)
- Long-sleeve linen shirt or lightweight sweater
- Dark jeans or hiking pants
- Waterproof walking shoes or trail sneakers
- Compact umbrella or rain hat
What to pack for Seattle in September
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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→Things worth doing
Hike around Mount Rainier, explore Pike Place Market and waterfront, visit Discovery Park for views and trails, kayak Lake Union, catch live music at Capitol Hill venues.
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 a ten-year climate record.
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 time to visit Seattle?
Is September a good time to visit Seattle?
Yes — it is a good time to visit, with pleasant, comfortable weather. In September, Seattle averages a high of 21°C (70°F) and a low of 13°C (55°F), with 60mm of rainfall across roughly 9 rainy days.
Q02What is the average temperature in Seattle in September?
What is the average temperature in Seattle 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 ten years of daily records (2015–2024, Open-Meteo Archive).
Q03How many rainy days does Seattle have in September?
How many rainy days does Seattle have in September?
Seattle averages approximately 9 rainy days in September, with a total monthly rainfall of about 60mm. This is based on daily precipitation records where days with 1mm or more of rain are counted as rainy days.
Q04What should I pack for Seattle in September?
What should I pack for Seattle in September?
For Seattle in September, pack layered clothing for changing temperatures, a compact umbrella or waterproof jacket, sunscreen and sunglasses, comfortable walking shoes. These recommendations are based on the ten-year weather averages for this specific month.
Q05How crowded is Seattle in September?
How crowded is 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.