Franklin County (Tri-Cities)
September
Weather in Franklin County, Washington for September 2026
Your guide to Franklin County weather in September - trends and predictions
Until now, September 2026 in Franklin County is cooler than usual, with temperatures averaging 25.7 °F, this is 4 °F below the typical seasonal average.
The forecast for the next days in Franklin County predicts temperatures to be around 23 °F, close to the historical average.
In general, the average temperature in Franklin County at the beginning of September is 32.4 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 20.3 °F by the end of September.
With an average of 5 rainy days, Franklin County experiences minimal rainfall in September.
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Temperatures
Rain 🌧️
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25
Dry days
5
Rainy days
0
Snow days
28°/14°
Temperatures
18 km/h
Avg max wind
44 %
Avg humidity
Franklin County Weather September
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Temperatures trend during September in Franklin County
See the weather trend as well as the moving average line
September weather in Franklin County day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Light rain | 34° /16° | 1.9 mm | 6 | |
| Sept. 2 |  Patchy rain possible | 34° /16° | 0.2 mm | 6 | |
| Sept. 3 |  Overcast | 32° /16° | 0.2 mm | 7 | |
| Sept. 4 |  Sunny | 32° /14° | 0 mm | 7 | |
| Sept. 5 | Sunny | 32° /16° | 0.3 mm | 7 | |
| Sept. 6 | Sunny | 31° /15° | 2.6 mm | 6 | |
| Sept. 7 | Sunny | 32° /16° | 0.2 mm | 7 | |
| Sept. 8 | Sunny | 32° /15° | 0 mm | 8 | |
| Sept. 9 | Sunny | 30° /15° | 0 mm | 7 | |
| Sept. 10 | Overcast | 32° /15° | 0 mm | 6 | |
| Sept. 11 | Overcast | 26° /15° | 2 mm | 5 | |
| Sept. 12 | Overcast | 28° /13° | 1.4 mm | 5 | |
| Sept. 13 | Sunny | 26° /13° | 0.9 mm | 6 | |
| Sept. 14 | Sunny | 25° /13° | 1.2 mm | 6 | |
| Sept. 15 | Sunny | 26° /12° | 0 mm | 6 | |
| Sept. 16 | Sunny | 29° /13° | 0 mm | 7 | |
| Sept. 17 | Overcast | 27° /14° | 0.1 mm | 6 | |
| Sept. 18 | Overcast | 28° /13° | 0 mm | 6 | |
| Sept. 19 | Overcast | 29° /12° | 0 mm | 7 | |
| Sept. 20 | Sunny | 26° /12° | 0.4 mm | 6 | |
| Sept. 21 | Sunny | 31° /19° | 0 mm | 4.8 | |
| Sept. 22 | Overcast | 27° /17° | 0 mm | 4.2 | |
| Sept. 23 | Overcast | 25° /14° | 0 mm | 3.9 | |
| Sept. 24 | Overcast | 25° /15° | 0 mm | 4 | |
| Sept. 25 | Sunny | 20° /13° | 1 mm | 4 | |
| Sept. 26 | Sunny | 20° /10° | 0 mm | 6 | |
| Sept. 27 | Overcast | 18° /12° | 0 mm | 5 | |
| Sept. 28 | Sunny | 20° /11° | 0 mm | 5 | |
| Sept. 29 | Sunny | 20° /11° | 0.1 mm | 6 | |
| Sept. 30 | Sunny | 19° /9° | 0 mm | 5 | |
| Next | |||||
Important Notice
Our weather forecast for Franklin 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 Franklin County forecast closer to your planned date for the most up-to-date weather information.
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Franklin County in September - FAQ
What are the expected maximum and minimum temperatures in Franklin County during September?
Enjoy moderate daytime temperatures of up to 28° and cooler nights around 14°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Franklin County during September?
Expect minimal rainfall in Franklin County during September, with a total of 11.1 mm over approximately 5 days. This minimal precipitation is unlikely to significantly impact plans.
What are the typical wind conditions in Franklin County during September?
The average wind speed in Franklin County during September is 18 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Franklin County
Explore the daily rainfall trends and prepare for Franklin Countys September weather 💧
Typically, Franklin County has 5 rainy days in September with a total of 11.1 mm of rainfall.
UV exposure in Franklin County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Where is Franklin County?Get accurate weather forecasts for Franklin County, located at latitude 46.245 and longitude -119.196. Stay updated with localized weather information tailored for Franklin County.
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