Sonoma Weather in September

What's the weather like in Sonoma (California) in September 2025?

The climate in Sonoma during September can be summarized as warm and very dry.

September is in the fall / autumn in Sonoma and is typically the 3rd warmest month of the year. Daytime maximum temperatures average around a comfortable 26°C (80°F), whilst at night 11°C (51°F) is normal.

Sonoma weather averages (imperial / metric)
Daytime temperature 26.4°C 79.5°F
Nightly temperature 10.8°C 51.4°F
Average temperature 18.6°C 65.5°F
Daily sunshine 10.5 hrs
Avg rainfall 9 mm 0.4 ins
Rainy days 2 days
Sea temperature 14.4°C 57.9°F
Humidity 66%
Windspeed 15.1kph 9 mph

On average September is the 4th driest month of the year in Sonoma with around 9mm 0.4 inches of rain making it a very dry time to visit.

On the flip side this corresponds to an average of 10.5 hours of sunshine per day.

September temperatures in Sonoma

Sonoma average temperature in September

September rainfall

Sonoma average rain in September

September hourly sunshine

Sonoma average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Sonoma in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Sonoma weather stats

Sonoma weather statistics
Hottest month: August 26.7°C 80.1°F
Driest month: July 1mm 0ins
Sunniest month: April 11.2hrs
Coldest month: January 13.1°C 55.6°F
Wettest month: January 172mm 6.8ins
Map showing location of Sonoma (38.29186, -122.45804) Sonoma map pin © Google

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