Sunnyvale
September
Weather in Sunnyvale for September 2025
Your guide to Sunnyvale weather in September - trends and predictions
In general, the average temperature in Sunnyvale at the beginning of September is 28.7 °F. As the month progressed, temperatures tended to moderately fall, reaching an average of 26.9 °F by the end of September.
Precipitation in Sunnyvale during September is a rare event, with an average of fewer than 2 rainy days.
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29
Dry days
1
Rainy days
0
Snow days
26°/13°
Temperatures
12 km/h
Avg max wind
67 %
Avg humidity
Sunnyvale in September average weather
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| Mon. | Tue. | Wed. | Thu. | Fri. | Sat. | Sun. |
|---|---|---|---|---|---|---|
| 1  24° | 2  25° | 3 29° | 4  31° | 5 31° | 6  32° | 7 29° |
| 8 30° | 9 30° | 10 28° | 11 26° | 12 27° | 13 29° | 14 29° |
| 15 25° | 16 23° | 17 20° | 18 23° | 19 25° | 20 25° | 21 27° |
| 22 28° | 23 29° | 24 29° | 25 26° | 26 25° | 27 29° | 28 27° |
| 29 26° | 30  26° |
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Temperatures trend during September in Sunnyvale
See the weather trend as well as the moving average line
September weather day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 | Overcast | 24° /14° | 0 mm | 6 | |
| Sept. 2 | Cloudy | 25° /13° | 0 mm | 7 | |
| Sept. 3 | Overcast | 29° /14° | 0 mm | 7 | |
| Sept. 4 | Mist | 31° /15° | 0 mm | 7 | |
| Sept. 5 | Overcast | 31° /14° | 0 mm | 7 | |
| Sept. 6 | Partly cloudy | 32° /15° | 0 mm | 8 | |
| Sept. 7 | Partly cloudy | 29° /14° | 0 mm | 8 | |
| Sept. 8 | Partly cloudy | 30° /14° | 0 mm | 8 | |
| Sept. 9 | Cloudy | 30° /13° | 0 mm | 7 | |
| Sept. 10 | Mist | 28° /12° | 0 mm | 7 | |
| Sept. 11 | Mist | 26° /12° | 0 mm | 6 | |
| Sept. 12 | Overcast | 27° /13° | 0 mm | 7 | |
| Sept. 13 | Mist | 29° /13° | 0 mm | 7 | |
| Sept. 14 | Cloudy | 29° /13° | 0 mm | 7 | |
| Sept. 15 | Cloudy | 25° /13° | 0 mm | 6 | |
| Sept. 16 | Overcast | 23° /14° | 0.7 mm | 5 | |
| Sept. 17 | Overcast | 20° /13° | 0 mm | 5 | |
| Sept. 18 | Mist | 23° /13° | 0 mm | 5 | |
| Sept. 19 | Mist | 25° /13° | 0 mm | 6 | |
| Sept. 20 | Mist | 25° /13° | 0 mm | 6 | |
| Sept. 21 | Partly cloudy | 27° /12° | 0 mm | 7 | |
| Sept. 22 | Mist | 28° /13° | 0 mm | 7 | |
| Sept. 23 | Overcast | 29° /13° | 0 mm | 7 | |
| Sept. 24 | Overcast | 29° /15° | 0 mm | 7 | |
| Sept. 25 | Mist | 26° /13° | 0 mm | 7 | |
| Sept. 26 | Overcast | 25° /13° | 0 mm | 6 | |
| Sept. 27 | Mist | 29° /12° | 0 mm | 7 | |
| Sept. 28 | Mist | 27° /12° | 0 mm | 7 | |
| Sept. 29 | Partly cloudy | 26° /12° | 0 mm | 7 | |
| Sept. 30 | Light rain shower | 26° /13° | 0.9 mm | 6 | |
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Important Notice
Our weather forecast for Sunnyvale 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 Sunnyvale forecast closer to your planned date for the most up-to-date weather information.
Sunnyvale in September - FAQ
What are the expected maximum and minimum temperatures in Sunnyvale during September?
Enjoy moderate daytime temperatures of up to 26° and cooler nights around 13°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Sunnyvale during September?
Rainfall in Sunnyvale during September is rare to nonexistent, with the total expected rainfall being less than 10 mm and approximately 1 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 Sunnyvale during September?
The average wind speed in Sunnyvale during September is 12 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Sunnyvale
Explore the daily rainfall trends and prepare for Sunnyvales September weather 💧
UV exposure in Sunnyvale during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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