Seattle (WA)
September
Weather in Seattle, Washington for September 2025
Your guide to Seattle weather in September - trends and predictions
Until now, September 2025 in Seattle is slightly cooler than the historical average by -1.9 °F.
Expect cooler weather in the next days in Seattle with the forecast suggesting a temperature of 20.7 °F, lower than the historical average.
In general, the average temperature in Seattle at the beginning of September is 25.7 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 19 °F by the end of September.
The climate of Seattle in September is notably wet, with an average of 14 rainy days, and a total of 55.2 mm of precipitation.
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Temperatures
Rain 🌧️
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16
Dry days
14
Rainy days
0
Snow days
22°/11°
Temperatures
11 km/h
Avg max wind
69 %
Avg humidity
Seattle Weather September
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Temperatures trend during September in Seattle
See the weather trend as well as the moving average line
September weather in Seattle day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Partly cloudy | 25° /12° | 0 mm | 6 | |
| Sept. 2 |  Sunny | 27° /12° | 0 mm | 7 | |
| Sept. 3 |  Overcast | 25° /13° | 0 mm | 6 | |
| Sept. 4 |  Mist | 25° /12° | 0.2 mm | 6 | |
| Sept. 5 | Overcast | 27° /14° | 0.3 mm | 7 | |
| Sept. 6 | Sunny | 26° /12° | 0.6 mm | 6 | |
| Sept. 7 | Partly cloudy | 25° /12° | 0 mm | 6 | |
| Sept. 8 | Partly cloudy | 25° /12° | 0.1 mm | 6 | |
| Sept. 9 | Overcast | 24° /12° | 0 mm | 6 | |
| Sept. 10 |  Patchy rain possible | 25° /11° | 0 mm | 6 | |
| Sept. 11 | Overcast | 20° /13° | 0.9 mm | 5 | |
| Sept. 12 | Patchy rain possible | 21° /12° | 0.6 mm | 5 | |
| Sept. 13 | Sunny | 26° /14° | 0 mm | 1.2 | |
| Sept. 14 | Patchy rain possible | 17° /13° | 4.6 mm | 0.2 | |
| Sept. 15 | Partly cloudy | 21° /14° | 0 mm | 1.1 | |
| Sept. 16 | Sunny | 31° /11° | 0 mm | 1.1 | |
| Sept. 17 | Sunny | 24° /12° | 0 mm | 0 | |
| Sept. 18 | Overcast | 20° /9° | 0 mm | 3 | |
| Sept. 19 | Sunny | 23° /10° | 0 mm | 5 | |
| Sept. 20 |  Cloudy | 17° /11° | 0.1 mm | 3 | |
| Sept. 21 | Patchy rain possible | 17° /14° | 0.5 mm | 4 | |
| Sept. 22 | Patchy rain possible | 16° /13° | 2.1 mm | 3 | |
| Sept. 23 | Patchy rain possible | 15° /13° | 2.7 mm | 3 | |
| Sept. 24 | Partly cloudy | 27° /14° | 0 mm | 5 | |
| Sept. 25 | Patchy rain possible | 17° /12° | 4.3 mm | 3 | |
| Sept. 26 | Patchy rain possible | 19° /11° | 0.4 mm | 3 | |
| Sept. 27 |  Heavy rain at times | 20° /10° | 4.7 mm | 5 | |
| Sept. 28 | Heavy rain at times | 16° /10° | 5.2 mm | 4 | |
| Sept. 29 |  Moderate rain at times | 17° /9° | 0.8 mm | 4 | |
| Sept. 30 | Moderate or heavy rain shower | 17° /7° | 4.5 mm | 4 | |
| Next | |||||
Important Notice
Our weather forecast for Seattle in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Seattle forecast closer to your planned date for the most up-to-date weather information.
Change Month
Seattle in September - FAQ
What are the expected maximum and minimum temperatures in Seattle during September?
Enjoy moderate daytime temperatures of up to 22° and cooler nights around 11°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Seattle during September?
Moderate rainfall is anticipated in Seattle during September, with a total of 55.2 mm spread over approximately 14 days. Considering plans for rainy days is advisable.
What are the typical wind conditions in Seattle during September?
The average wind speed in Seattle during September is 11 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Seattle
Explore the daily rainfall trends and prepare for Seattles September weather 💧
UV exposure in Seattle during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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