Sonoma County (Santa Rosa)
September
Weather in Sonoma County, California for September 2027
Your guide to Sonoma County weather in September - trends and predictions
In general, the average temperature in Sonoma County at the beginning of September is 25.9 °C. As the month progressed, temperatures tended to moderately fall, reaching an average of 25.1 °C by the end of September.
Precipitation in Sonoma County during September is a rare event, with an average of fewer than 2 rainy days.
Is September a good time to visit Sonoma County? check out the best time to travel to Sonoma County page.
✨ Is September a good time to visit Sonoma County? – Ask the AI Weatherman
Temperatures
Rain 🌧️
More
29
Dry days
1
Rainy days
0
Snow days
26°/11°
Temperatures
15 km/h
Avg max wind
69 %
Avg humidity
Sonoma County Weather September
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Temperatures trend during September in Sonoma County
See the weather trend as well as the moving average line
September weather in Sonoma County day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Mist | 24° /12° | 0 mm | 6 | |
| Sept. 2 |  Light rain | 23° /12° | 7.9 mm | 5 | |
| Sept. 3 |  Moderate rain | 25° /12° | 14.8 mm | 5 | |
| Sept. 4 |  Sunny | 28° /12° | 0 mm | 7 | |
| Sept. 5 | Sunny | 28° /12° | 0 mm | 7 | |
| Sept. 6 | Mist | 27° /11° | 0 mm | 7 | |
| Sept. 7 | Mist | 27° /10° | 0 mm | 7 | |
| Sept. 8 | Sunny | 28° /11° | 0 mm | 7 | |
| Sept. 9 | Mist | 28° /13° | 0 mm | 5 | |
| Sept. 10 |  Cloudy | 26° /12° | 0 mm | 6 | |
| Sept. 11 | Sunny | 27° /12° | 0 mm | 7 | |
| Sept. 12 | Cloudy | 27° /11° | 0 mm | 7 | |
| Sept. 13 | Sunny | 27° /12° | 0 mm | 7 | |
| Sept. 14 | Sunny | 28° /12° | 0 mm | 7 | |
| Sept. 15 | Mist | 27° /11° | 0 mm | 7 | |
| Sept. 16 |  Partly cloudy | 25° /11° | 0 mm | 7 | |
| Sept. 17 | Mist | 24° /11° | 0 mm | 6 | |
| Sept. 18 | Light rain | 24° /12° | 3.2 mm | 6 | |
| Sept. 19 | Mist | 24° /13° | 0 mm | 6 | |
| Sept. 20 | Mist | 22° /12° | 0 mm | 4 | |
| Sept. 21 | Mist | 24° /11° | 0 mm | 6 | |
| Sept. 22 | Partly cloudy | 26° /10° | 0 mm | 6 | |
| Sept. 23 | Partly cloudy | 30° /10° | 0 mm | 6.7 | |
| Sept. 24 | Mist | 26° /12° | 0 mm | 5 | |
| Sept. 25 | Mist | 22° /12° | 0.3 mm | 5 | |
| Sept. 26 |  Patchy rain possible | 26° /12° | 1.3 mm | 5 | |
| Sept. 27 | Sunny | 27° /11° | 0 mm | 6 | |
| Sept. 28 | Partly cloudy | 23° /11° | 0 mm | 5 | |
| Sept. 29 | Cloudy | 26° /12° | 0 mm | 5 | |
| Sept. 30 | Patchy rain possible | 25° /13° | 0 mm | 6 | |
| Next | |||||
Important Notice
Our weather forecast for Sonoma 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 Sonoma County forecast closer to your planned date for the most up-to-date weather information.
Change Month
Sonoma County in September - FAQ
What are the expected maximum and minimum temperatures in Sonoma County during September?
Enjoy moderate daytime temperatures of up to 26° and cooler nights around 11°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Sonoma County during September?
In September, Sonoma County can expect light to moderate rainfall, totaling 27.6 mm across approximately 1 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Sonoma County during September?
The average wind speed in Sonoma County during September is 15 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Sonoma County
Explore the daily rainfall trends and prepare for Sonoma Countys September weather 💧
Typically, Sonoma County has 1 rainy days in September with a total of 27.6 mm of rainfall.
UV exposure in Sonoma County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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