Napa Weather in September

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

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

September is in the fall / autumn in Napa and is typically the 3rd warmest month of the year. Daytime maximum temperatures average around a comfortable 27°C (80°F), whilst at night 11°C (52°F) is normal.

Napa weather averages (imperial / metric)
Daytime temperature 26.8°C 80.2°F
Nightly temperature 11.2°C 52.2°F
Average temperature 19°C 66.2°F
Daily sunshine 10.7 hrs
Avg rainfall 10 mm 0.4 ins
Rainy days 2 days
Sea temperature 14.4°C 57.9°F
Humidity 65%
Windspeed 15.1kph 9 mph

On average September is the 4th driest month of the year in Napa with around 10mm 0.4 inches of rain making it a very dry time to visit.

On the flip side this corresponds to an average of 10.7 hours of sunshine per day.

September temperatures in Napa

Napa average temperature in September

September rainfall

Napa average rain in September

September hourly sunshine

Napa 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 Napa 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

Napa weather stats

Napa weather statistics
Hottest month: July 27.7°C 81.9°F
Driest month: July 1mm 0ins
Sunniest month: May 12.2hrs
Coldest month: January 12.6°C 54.7°F
Wettest month: January 157mm 6.2ins
Map showing location of Napa (38.29714, -122.28553) Napa map pin © Google

Locations nearby

Top United States locations