Rancho Cucamonga Weather in September

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

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

September is in the fall / autumn in Rancho Cucamonga and is typically the 3rd warmest month of the year. Daytime maximum temperatures average around a comfortable 31°C (88°F), whilst at night 15°C (58°F) is normal.

Rancho Cucamonga weather averages (imperial / metric)
Daytime temperature 31°C 87.7°F
Nightly temperature 14.5°C 58°F
Average temperature 22.7°C 72.9°F
Daily sunshine 10.2 hrs
Avg rainfall 9 mm 0.4 ins
Rainy days 2 days
Sea temperature 19.6°C 67.3°F
Humidity 62%
Windspeed 12.6kph 8 mph

On average September is the 5th driest month of the year in Rancho Cucamonga 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 10.2 hours of sunshine per day.

September temperatures in Rancho Cucamonga

Rancho Cucamonga average temperature in September

September rainfall

Rancho Cucamonga average rain in September

September hourly sunshine

Rancho Cucamonga 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 Rancho Cucamonga 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

Rancho Cucamonga weather stats

Rancho Cucamonga weather statistics
Hottest month: August 33.2°C 91.8°F
Driest month: July 1mm 0ins
Sunniest month: August 11.7hrs
Coldest month: January 18.2°C 64.8°F
Wettest month: January 84mm 3.3ins
Map showing location of Rancho Cucamonga (34.1064, -117.59311) Rancho Cucamonga map pin © Google

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