Washington (Seattle)
September
Weather in Washington for September 2025
Your guide to Washington weather in September - trends and predictions
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Until now, September 2025 in Washington is slightly cooler than the historical average by -1.8 °F.
Expect cooler weather in the next days in Washington with the forecast suggesting a temperature of 21.7 °F, lower than the historical average.
In general, the average temperature in Washington at the beginning of September is 25.7 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 17.9 °F by the end of September.
The climate of Washington 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
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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
Washington Weather September
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What’s the Weather Like in Washington This September?
Discover the average temperatures and weather trends across Washington’s cities this September.
Temperatures trend during September in Washington
See the weather trend as well as the moving average line
September weather in Washington 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 | Mist | 21° /11° | 0.2 mm | 5 | |
| Sept. 14 | Patchy rain possible | 21° /10° | 2.5 mm | 5 | |
| Sept. 15 | Partly cloudy | 21° /14° | 0 mm | 1.2 | |
| Sept. 16 | Sunny | 34° /13° | 0 mm | 1.1 | |
| Sept. 17 | Sunny | 27° /16° | 0 mm | 1.2 | |
| Sept. 18 | Partly cloudy | 23° /12° | 0 mm | 1.1 | |
| Sept. 19 | Sunny | 25° /11° | 0 mm | 0 | |
| Sept. 20 | Patchy rain possible | 15° /10° | 0.2 mm | 3 | |
| Sept. 21 | Patchy rain possible | 22° /13° | 0.1 mm | 4 | |
| Sept. 22 | Patchy rain possible | 22° /12° | 0.3 mm | 4 | |
| Sept. 23 | Sunny | 24° /10° | 0 mm | 5 | |
| Sept. 24 | Patchy rain possible | 21° /13° | 2.7 mm | 3 | |
| Sept. 25 | Partly cloudy | 19° /11° | 0 mm | 4 | |
| Sept. 26 | Partly cloudy | 16° /8° | 0 mm | 4 | |
| Sept. 27 | Sunny | 21° /9° | 0 mm | 4 | |
| Sept. 28 |  Moderate rain | 14° /11° | 8.9 mm | 3 | |
| 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 Washington 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 Washington forecast closer to your planned date for the most up-to-date weather information.
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Washington in September - FAQ
What are the expected maximum and minimum temperatures in Washington 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 Washington during September?
Moderate rainfall is anticipated in Washington 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 Washington during September?
The average wind speed in Washington during September is 11 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Washington
Explore the daily rainfall trends and prepare for Washingtons September weather 💧
UV exposure in Washington during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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