Rialto Weather in September

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

The climate in Rialto during September can be summarized as hot and very dry.

September is in the fall / autumn in Rialto and is typically the 3rd warmest month of the year. Daytime maximum temperatures average around a comfortable 32°C (89°F), whilst at night 15°C (59°F) is normal.

Rialto weather averages (imperial / metric)
Daytime temperature 31.8°C 89.2°F
Nightly temperature 14.9°C 58.7°F
Average temperature 23.3°C 73.9°F
Daily sunshine 10.3 hrs
Avg rainfall 9 mm 0.4 ins
Rainy days 1 days
Sea temperature 19.6°C 67.3°F
Humidity 60%
Windspeed 13kph 8 mph

On average September is the 4th driest month of the year in Rialto 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 10.3 hours of sunshine per day.

September temperatures in Rialto

Rialto average temperature in September

September rainfall

Rialto average rain in September

September hourly sunshine

Rialto 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 Rialto 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

Rialto weather stats

Rialto weather statistics
Hottest month: August 34.1°C 93.4°F
Driest month: July 1mm 0ins
Sunniest month: August 11.8hrs
Coldest month: January 18.5°C 65.3°F
Wettest month: January 78mm 3.1ins
Map showing location of Rialto (34.1064, -117.37032) Rialto map pin © Google

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