Weather in Sunnyvale, California for September 2025
Until now, September 2025 in Sunnyvale is cooler than usual, with temperatures averaging 22.6 °F, this is -4.2 °F below the typical seasonal average.
The forecast for the upcoming days in Sunnyvale predicts a temperature of 28.7 °F, which is slightly above the historical average.
In general, the average temperature in Sunnyvale at the beginning of September is 27.7 °F. As the month progressed, temperatures tended to moderately fall, reaching an average of 26.3 °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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Sunnyvale Weather September
Temperatures trend during September in Sunnyvale
September weather in Sunnyvale day by day
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Overcast | 26° /14° | 0 mm | 7 | |
| Sept. 2 |  Sunny | 26° /14° | 0 mm | 7 | |
| Sept. 3 | Overcast | 29° /14° | 0 mm | 7 | |
| Sept. 4 |  Mist | 30° /14° | 0 mm | 7 | |
| Sept. 5 | Overcast | 27° /14° | 0 mm | 6 | |
| Sept. 6 |  Partly cloudy | 29° /14° | 0 mm | 7 | |
| Sept. 7 | Partly cloudy | 27° /15° | 0 mm | 7 | |
| Sept. 8 | Partly cloudy | 27° /14° | 0 mm | 7 | |
| Sept. 9 |  Cloudy | 26° /14° | 0 mm | 6 | |
| Sept. 10 | Mist | 25° /13° | 1.3 mm | 6 | |
| Sept. 11 | Mist | 24° /13° | 0 mm | 5 | |
| Sept. 12 | Overcast | 26° /13° | 0 mm | 6 | |
| Sept. 13 | Mist | 26° /13° | 0 mm | 6 | |
| Sept. 14 | Cloudy | 28° /14° | 0 mm | 6 | |
| Sept. 15 | Sunny | 34° /13° | 0 mm | 1.8 | |
| Sept. 16 | Sunny | 35° /17° | 0 mm | 1.7 | |
| Sept. 17 | Sunny | 35° /16° | 0 mm | 1.4 | |
| Sept. 18 |  Patchy rain possible | 24° /17° | 0.6 mm | 0.8 | |
| Sept. 19 | Patchy rain possible | 22° /18° | 3.3 mm | 0 | |
| Sept. 20 | Overcast | 27° /17° | 0 mm | 5 | |
| Sept. 21 | Sunny | 30° /16° | 0 mm | 6 | |
| Sept. 22 | Sunny | 33° /17° | 0 mm | 6 | |
| Sept. 23 | Sunny | 30° /19° | 0 mm | 6 | |
| Sept. 24 | Sunny | 26° /16° | 0 mm | 6 | |
| Sept. 25 | Sunny | 25° /13° | 0 mm | 5 | |
| Sept. 26 | Sunny | 26° /12° | 0 mm | 5 | |
| Sept. 27 | Sunny | 30° /13° | 0 mm | 5 | |
| Sept. 28 | Sunny | 25° /13° | 0 mm | 5 | |
| Sept. 29 | Partly cloudy | 26° /12° | 0 mm | 7 | |
| Sept. 30 | Light rain shower | 26° /13° | 0.9 mm | 6 | |
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Sunnyvale in September - FAQ
September rainfall patterns in Sunnyvale
UV exposure in Sunnyvale during September
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Where is Sunnyvale?Get accurate weather forecasts for Sunnyvale, located at latitude 37.369 and longitude -122.036. Stay updated with localized weather information tailored for Sunnyvale.