Last updated: June 24, 2025
In December, the average temperature in Santa Rosa, United States hovers around 5°C (42°F). Expect a wide temperature range, with minimums dropping to -16°C (3°F) and maximums soaring to 23°C (74°F). Additionally, anticipate about 11 mm (0.4 in) of precipitation spread over 2 days and an average humidity level of 77%.
In December in Santa Rosa, the average temperature is 5°C (42°F). The maximum can reach 23°C (74°F), while the minimum can dip as low as -16°C (3°F). It's essential to be prepared for a wide range of temperatures if you're planning to travel during this time.
In Santa Rosa in December, the precipitation amount is 11 mm (0.4 in) over the course of 2 days.
In Santa Rosa in December, humidity is 77%. With an average temperature of 5°C (42°F), this humidity feels like a chilly, damp embrace, making outdoor activities feel quite uncomfortable and the air heavy as you traverse the landscape.
In Santa Rosa in December, the maximum UV index reaches 4, which corresponds to a moderate Exposure Category. With a time to burn of 30 minutes, it’s important to take precautions to protect your skin. You can find more details in the Hourly UV Index in Santa Rosa for better planning.
UV Risk Categories
Weather in Santa Rosa varies notably across the year, with each month offering distinct climate conditions. This page compares December’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 |