Umatilla County (Pendleton)
September
Weather in Umatilla County, Oregon for September 2026
Your guide to Umatilla County weather in September - trends and predictions
Until now, September 2026 in Umatilla County is cooler than usual, with temperatures averaging 23.1 °F, this is 3.3 °F below the typical seasonal average.
The forecast for the next days in Umatilla County predicts temperatures to be around 22 °F, close to the historical average.
In general, the average temperature in Umatilla County at the beginning of September is 29 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 20.4 °F by the end of September.
With an average of 3 rainy days, Umatilla County experiences minimal rainfall in September.
New! Chat with our AI weatherman - it’s amazing and free.
Temperatures
Rain 🌧️
More
27
Dry days
3
Rainy days
0
Snow days
28°/15°
Temperatures
17 km/h
Avg max wind
44 %
Avg humidity
Umatilla County Weather September
Move between months or click on a day
Temperatures trend during September in Umatilla County
See the weather trend as well as the moving average line
September weather in Umatilla County day by day
Click on a date for more information
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 32° /15° | 0 mm | 5 | |
| Sept. 2 | Sunny | 32° /16° | 2.1 mm | 5 | |
| Sept. 3 |  Partly cloudy | 28° /17° | 38.7 mm | 5 | |
| Sept. 4 | Partly cloudy | 30° /14° | 0.9 mm | 8 | |
| Sept. 5 | Partly cloudy | 29° /15° | 0 mm | 7 | |
| Sept. 6 |  Cloudy | 25° /14° | 9.8 mm | 5 | |
| Sept. 7 | Sunny | 27° /14° | 0.4 mm | 6 | |
| Sept. 8 |  Overcast | 27° /12° | 0 mm | 7 | |
| Sept. 9 |  Thundery outbreaks possible | 24° /12° | 1.4 mm | 6 | |
| Sept. 10 | Thundery outbreaks possible | 28° /12° | 0 mm | 5 | |
| Sept. 11 | Thundery outbreaks possible | 25° /13° | 4 mm | 5 | |
| Sept. 12 | Sunny | 25° /10° | 3.5 mm | 4 | |
| Sept. 13 | Sunny | 23° /13° | 3.4 mm | 5 | |
| Sept. 14 |  Patchy light rain | 19° /12° | 0.7 mm | 5 | |
| Sept. 15 | Sunny | 22° /9° | 0.1 mm | 4 | |
| Sept. 16 | Sunny | 25° /11° | 0.2 mm | 6 | |
| Sept. 17 | Sunny | 31° /14° | 0 mm | 8 | |
| Sept. 18 | Sunny | 23° /17° | 0.2 mm | 4.9 | |
| Sept. 19 | Sunny | 25° /17° | 0 mm | 5 | |
| Sept. 20 | Overcast | 27° /18° | 0 mm | 5 | |
| Sept. 21 | Sunny | 26° /19° | 0 mm | 5.4 | |
| Sept. 22 | Overcast | 22° /16° | 0 mm | 6 | |
| Sept. 23 | Sunny | 22° /15° | 0 mm | 6 | |
| Sept. 24 | Overcast | 25° /17° | 0 mm | 7 | |
| Sept. 25 | Overcast | 20° /14° | 0 mm | 5 | |
| Sept. 26 | Overcast | 18° /11° | 0 mm | 5 | |
| Sept. 27 | Overcast | 18° /13° | 0 mm | 5 | |
| Sept. 28 | Sunny | 21° /13° | 0 mm | 6 | |
| Sept. 29 | Overcast | 19° /16° | 0 mm | 4 | |
| Sept. 30 | Overcast | 22° /15° | 0 mm | 5 | |
| Next | |||||
Important Notice
Our weather forecast for Umatilla 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 Umatilla County forecast closer to your planned date for the most up-to-date weather information.
Change Month
Umatilla County in September - FAQ
What are the expected maximum and minimum temperatures in Umatilla County during September?
During September, expect a variety of temperatures with highs around 28° and lows near 15°, suitable for diverse activities and preferences.
How much rainfall should be expected in Umatilla County during September?
Rainfall in Umatilla County during September is rare to nonexistent, with the total expected rainfall being less than 10 mm and approximately 3 days seeing any precipitation. Planning without the concern for rain is generally straightforward during this very dry period.
What are the typical wind conditions in Umatilla County during September?
The average wind speed in Umatilla County during September is 17 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Umatilla County
Explore the daily rainfall trends and prepare for Umatilla Countys September weather 💧
Typically, Umatilla County has 3 rainy days in September with a total of 9.5 mm of rainfall.
UV exposure in Umatilla County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
Top locations in Umatilla County
Select a location for an accurate weather forecast
More Locations Quick links
More Umatilla County weather pages
You are here
Where is Umatilla County?Get accurate weather forecasts for Umatilla County, located at latitude 45.672 and longitude -118.789. Stay updated with localized weather information tailored for Umatilla County.
Found a mistake?
We appreciate your attention to details. Tell us here.