Last updated: June 24, 2025
In September, the average temperature in Mountain View, United States is a pleasant 19°C (66°F). However, be prepared for a range of temperatures, with lows dipping to -2°C (30°F) and highs potentially soaring to 36°C (98°F). Expect about 29 mm (1.2 in) of precipitation spread over 5 days, and enjoy an average humidity level of 65%. Whether you’re embracing the heat or seeking cool relief, Mountain View during this month offers a unique climate experience.
In September in Mountain View, the average temperature is 19°C (66°F). Maximum temperatures can reach 36°C (98°F), while minimums can drop as low as -2°C (30°F). Travelers should be prepared for a wide range of temperatures and plan accordingly for both warm days and chilly nights.
In Mountain View in September, the precipitation amount is 29 mm (1.2 in) over a period of 5 days.
In Mountain View in September humidity is 65%. With an average temperature of 19°C (66°F), this humidity feels like a warm embrace, making outdoor activities refreshing but slightly sticky, so it's advisable to stay hydrated and take breaks in shaded areas while exploring.
In Mountain View in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more 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 | -1°C (31°F) | 23 mm (0.9 inches) | 88% | moderate |
| February Weather | -1°C (30°F) | 29 mm (1.1 inches) | 87% | high |
| March Weather | 4°C (40°F) | 57 mm (2.3 inches) | 81% | very high |
| April Weather | 8°C (47°F) | 55 mm (2.2 inches) | 76% | extreme |
| May Weather | 13°C (56°F) | 111 mm (4.4 inches) | 66% | extreme |
| June Weather | 20°C (68°F) | 48 mm (1.9 inches) | 58% | extreme |
| July Weather | 23°C (74°F) | 43 mm (1.7 inches) | 52% | extreme |
| August Weather | 22°C (72°F) | 35 mm (1.4 inches) | 56% | extreme |
| September Weather | 19°C (66°F) | 29 mm (1.2 inches) | 65% | very high |
| October Weather | 9°C (49°F) | 37 mm (1.5 inches) | 76% | high |
| November Weather | 5°C (41°F) | 24 mm (1.0 inches) | 82% | moderate |
| December Weather | 1°C (34°F) | 14 mm (0.6 inches) | 89% | moderate |