Last updated: June 24, 2025
In September, the average temperature in Mountain View, United States is a pleasant 23°C (75°F), making it an ideal time to explore. Visitors can expect temperatures to range from a cool 9°C (48°F) to a warm 35°C (96°F). However, be prepared for a bit of rain with an average precipitation of 82 mm (3.2 in) over about 7 days. The air is often humid, boasting an average humidity level of 71%.
In September in Mountain View, the average temperature is 23°C (75°F). Maximum temperatures can reach 35°C (96°F), while minimums can drop to as low as 9°C (48°F). This makes it an ideal time for travelers to enjoy a pleasant mix of warm days and cooler evenings in Mountain View.
In Mountain View in September, the precipitation amount is 82 mm (3.2 in) over the course of 7 days.
In Mountain View in September, humidity is 71%. With an average temperature of 23°C (75°F), this humidity feels like walking through a warm, damp blanket, making traveling quite sweaty and uncomfortable, especially during the midday sun.
In Mountain View in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Mountain View.
UV Risk Categories
Weather in Mountain View varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Mountain View, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 4°C (39°F) | 78 mm (3.1 inches) | 84% | moderate |
| February Weather | 6°C (42°F) | 131 mm (5.2 inches) | 83% | high |
| March Weather | 11°C (53°F) | 137 mm (5.4 inches) | 81% | very high |
| April Weather | 15°C (59°F) | 144 mm (5.7 inches) | 81% | very high |
| May Weather | 20°C (69°F) | 174 mm (6.9 inches) | 83% | extreme |
| June Weather | 25°C (77°F) | 100 mm (3.9 inches) | 83% | extreme |
| July Weather | 27°C (81°F) | 89 mm (3.5 inches) | 81% | extreme |
| August Weather | 26°C (79°F) | 116 mm (4.6 inches) | 74% | very high |
| September Weather | 23°C (75°F) | 82 mm (3.2 inches) | 71% | very high |
| October Weather | 17°C (62°F) | 103 mm (4.1 inches) | 76% | high |
| November Weather | 9°C (49°F) | 77 mm (3.0 inches) | 84% | moderate |
| December Weather | 7°C (45°F) | 97 mm (3.8 inches) | 88% | moderate |