California Weather in September

The climate in California during September can be summarized as warm, humid and damp.

September is in the fall / autumn in California and is typically the 4th warmest month of the year. Daytime maximum temperatures average around a muggy 27°C (80°F), whilst at night 14°C (57°F) is normal.

On average September is the 3rd wettest month of the year in California with around 101mm 4 inches of rain making it a damp time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 8.3 hours of sunshine per day.

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 California in September 2025.