Ontario (CA)
September
Weather in Ontario, California for September 2025
Your guide to Ontario weather in September - trends and predictions
Beach Hazards Statement - See hour by hour.
Until now, September 2025 in Ontario is slightly cooler than the historical average by -1.8 °F.
The forecast for the upcoming days in Ontario predicts a temperature of 32.8 °F, which is slightly above the historical average.
In general, the average temperature in Ontario at the beginning of September is 33.3 °F. As the month progressed, temperatures tended to moderately fall, reaching an average of 31.9 °F by the end of September.
With an average of 4 rainy days, Ontario experiences minimal rainfall in September.
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Temperatures
Rain 🌧️
More
26
Dry days
4
Rainy days
0
Snow days
29°/16°
Temperatures
15 km/h
Avg max wind
48 %
Avg humidity
Ontario Weather September
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Temperatures trend during September in Ontario
See the weather trend as well as the moving average line
September weather in Ontario day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Patchy rain possible | 34° /20° | 1.6 mm | 8 | |
| Sept. 2 |  Light rain | 33° /20° | 0.7 mm | 8 | |
| Sept. 3 | Light rain | 31° /19° | 2.3 mm | 7 | |
| Sept. 4 |  Sunny | 33° /19° | 0 mm | 8 | |
| Sept. 5 |  Partly cloudy | 33° /19° | 0 mm | 8 | |
| Sept. 6 | Sunny | 34° /21° | 0 mm | 9 | |
| Sept. 7 | Sunny | 35° /20° | 0 mm | 8 | |
| Sept. 8 | Partly cloudy | 35° /21° | 0 mm | 8 | |
| Sept. 9 | Sunny | 34° /20° | 0 mm | 8 | |
| Sept. 10 |  Overcast | 30° /18° | 0 mm | 7 | |
| Sept. 11 | Partly cloudy | 28° /16° | 0 mm | 7 | |
| Sept. 12 | Sunny | 27° /14° | 0 mm | 7 | |
| Sept. 13 | Sunny | 27° /14° | 0 mm | 7 | |
| Sept. 14 | Partly cloudy | 30° /14° | 0 mm | 7 | |
| Sept. 15 | Sunny | 36° /21° | 0 mm | 1.9 | |
| Sept. 16 | Sunny | 37° /23° | 0 mm | 2 | |
| Sept. 17 | Overcast | 32° /23° | 0 mm | 1.7 | |
| Sept. 18 |  Heavy rain | 26° /21° | 35.7 mm | 1.8 | |
| Sept. 19 | Patchy rain possible | 26° /22° | 4.3 mm | 0 | |
| Sept. 20 | Sunny | 30° /20° | 0 mm | 6 | |
| Sept. 21 | Sunny | 34° /21° | 0 mm | 7 | |
| Sept. 22 | Sunny | 36° /24° | 0 mm | 7 | |
| Sept. 23 | Sunny | 36° /25° | 0 mm | 7 | |
| Sept. 24 | Sunny | 37° /25° | 0 mm | 7 | |
| Sept. 25 | Sunny | 36° /25° | 0 mm | 7 | |
| Sept. 26 | Sunny | 33° /23° | 0 mm | 7 | |
| Sept. 27 | Sunny | 30° /20° | 0 mm | 6 | |
| Sept. 28 | Sunny | 30° /19° | 0 mm | 6 | |
| Sept. 29 | Sunny | 30° /16° | 0 mm | 8 | |
| Sept. 30 | Light rain shower | 27° /15° | 1.7 mm | 7 | |
| Next | |||||
Important Notice
Our weather forecast for Ontario in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Ontario forecast closer to your planned date for the most up-to-date weather information.
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Ontario in September - FAQ
What are the expected maximum and minimum temperatures in Ontario during September?
During September, expect a variety of temperatures with highs around 29° and lows near 16°, suitable for diverse activities and preferences.
How much rainfall should be expected in Ontario during September?
Rainfall in Ontario during September is rare to nonexistent, with the total expected rainfall being less than 10 mm and approximately 4 days seeing any precipitation. Planning without the concern for rain is generally straightforward during this very dry period.
What are the typical wind conditions in Ontario during September?
The average wind speed in Ontario during September is 15 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Ontario
Explore the daily rainfall trends and prepare for Ontarios September weather 💧
UV exposure in Ontario during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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