Last updated: June 24, 2025
In September, the average temperature in Santa Rosa, United States is a pleasant 22°C (72°F). However, be prepared for a range of temperatures, with minimums dipping to 3°C (37°F) and maximums soaring up to 37°C (99°F). During this month, you can expect about 33 mm (1.3 in) of precipitation over 5 days, while the average humidity sits at a comfortable 76%.
In September, in Santa Rosa, the average temperature is 22°C (72°F), with maximums reaching up to 37°C (99°F) and minimums dropping as low as 3°C (37°F). This range makes it essential for travelers to pack accordingly, ensuring comfort during both warm days and cool nights.
In Santa Rosa in September, the precipitation amount is 33 mm (1.3 in) over the course of 5 days.
In Santa Rosa in September humidity is 76%. With an average temperature of 22°C (72°F), this humidity feels like a warm embrace, making travel slightly uncomfortable as you navigate through the thick, saturated air.
In Santa Rosa in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Santa Rosa.
UV Risk Categories
Weather in Santa Rosa varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Santa Rosa, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 4°C (39°F) | 15 mm (0.6 inches) | 74% | moderate |
| February Weather | 6°C (43°F) | 12 mm (0.5 inches) | 75% | high |
| March Weather | 11°C (51°F) | 28 mm (1.1 inches) | 61% | very high |
| April Weather | 14°C (58°F) | 27 mm (1.1 inches) | 61% | extreme |
| May Weather | 20°C (68°F) | 30 mm (1.2 inches) | 69% | extreme |
| June Weather | 25°C (78°F) | 41 mm (1.6 inches) | 74% | extreme |
| July Weather | 26°C (80°F) | 31 mm (1.2 inches) | 75% | extreme |
| August Weather | 25°C (77°F) | 56 mm (2.2 inches) | 78% | extreme |
| September Weather | 22°C (72°F) | 33 mm (1.3 inches) | 76% | extreme |
| October Weather | 14°C (58°F) | 47 mm (1.9 inches) | 76% | very high |
| November Weather | 9°C (49°F) | 14 mm (0.6 inches) | 80% | moderate |
| December Weather | 5°C (42°F) | 11 mm (0.4 inches) | 77% | moderate |