Multnomah County (Portland)
September
Weather in Multnomah County for September 2025
Your guide to Multnomah County weather in September - trends and predictions
In general, the average temperature in Multnomah County at the beginning of September is 27.9 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 20.6 °F by the end of September.
Multnomah County sees moderate rainfall in September, averaging 10 rainy days.
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20
Dry days
10
Rainy days
0
Snow days
24°/12°
Temperatures
11 km/h
Avg max wind
63 %
Avg humidity
Multnomah County in September average weather
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| Mon. | Tue. | Wed. | Thu. | Fri. | Sat. | Sun. |
|---|---|---|---|---|---|---|
| 1  30° | 2  27° | 3  25° | 4  25° | 5 30° | 6  30° | 7 28° |
| 8 29° | 9 28° | 10  27° | 11 21° | 12 23° | 13 23° | 14 27° |
| 15 28° | 16 27° | 17 21° | 18 21° | 19 20° | 20 20° | 21 24° |
| 22 24° | 23 23° | 24  25° | 25 20° | 26 21° | 27 19° | 28 19° |
| 29 19° | 30 21° |
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Temperatures trend during September in Multnomah County
See the weather trend as well as the moving average line
September weather day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 | Fog | 30° /16° | 0.2 mm | 7 | |
| Sept. 2 | Cloudy | 27° /15° | 0.1 mm | 6 | |
| Sept. 3 | Patchy rain possible | 25° /15° | 1.2 mm | 6 | |
| Sept. 4 | Overcast | 25° /12° | 1.1 mm | 6 | |
| Sept. 5 | Overcast | 30° /13° | 0 mm | 7 | |
| Sept. 6 | Partly cloudy | 30° /15° | 0 mm | 8 | |
| Sept. 7 | Cloudy | 28° /15° | 0 mm | 6 | |
| Sept. 8 | Overcast | 29° /14° | 0 mm | 7 | |
| Sept. 9 | Cloudy | 28° /12° | 0 mm | 7 | |
| Sept. 10 | Sunny | 27° /13° | 0 mm | 7 | |
| Sept. 11 | Overcast | 21° /13° | 5.5 mm | 5 | |
| Sept. 12 | Cloudy | 23° /12° | 0.3 mm | 6 | |
| Sept. 13 | Overcast | 23° /11° | 0 mm | 6 | |
| Sept. 14 | Sunny | 27° /11° | 0.1 mm | 7 | |
| Sept. 15 | Sunny | 28° /12° | 0 mm | 7 | |
| Sept. 16 | Sunny | 27° /11° | 0 mm | 7 | |
| Sept. 17 | Overcast | 21° /11° | 6.1 mm | 5 | |
| Sept. 18 | Overcast | 21° /13° | 0 mm | 5 | |
| Sept. 19 | Overcast | 20° /12° | 0 mm | 5 | |
| Sept. 20 | Light rain shower | 20° /11° | 0.7 mm | 5 | |
| Sept. 21 | Partly cloudy | 24° /9° | 0 mm | 7 | |
| Sept. 22 | Sunny | 24° /12° | 0 mm | 7 | |
| Sept. 23 | Light rain shower | 23° /13° | 0.8 mm | 5 | |
| Sept. 24 | Light drizzle | 25° /13° | 2.2 mm | 6 | |
| Sept. 25 | Light rain shower | 20° /14° | 7 mm | 5 | |
| Sept. 26 | Light rain shower | 21° /12° | 5.3 mm | 5 | |
| Sept. 27 | Light rain shower | 19° /13° | 6.3 mm | 5 | |
| Sept. 28 | Patchy rain possible | 19° /11° | 0.2 mm | 5 | |
| Sept. 29 | Overcast | 19° /9° | 0 mm | 4 | |
| Sept. 30 | Partly cloudy | 21° /8° | 0 mm | 6 | |
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Important Notice
Our weather forecast for Multnomah County 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 Multnomah County forecast closer to your planned date for the most up-to-date weather information.
Multnomah County in September - FAQ
What are the expected maximum and minimum temperatures in Multnomah County during September?
Enjoy moderate daytime temperatures of up to 24° and cooler nights around 12°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Multnomah County during September?
In September, Multnomah County can expect light to moderate rainfall, totaling 50 mm across approximately 10 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Multnomah County during September?
The average wind speed in Multnomah County during September is 11 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Multnomah County
Explore the daily rainfall trends and prepare for Multnomah Countys September weather 💧
UV exposure in Multnomah County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Where is Multnomah County?Get accurate weather forecasts for Multnomah County, located at latitude 45.523 and longitude -122.676. Stay updated with localized weather information tailored for Multnomah County.
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