nomadseason

December Weather in Santa Rosa, United States

Last updated: June 24, 2025

In December, the average temperature in Santa Rosa, United States is a pleasant 18°C (65°F), with a minimum of 1°C (33°F) and a maximum reaching up to 34°C (93°F). Expect about 23 mm (0.9 in) of precipitation over 4 days, and enjoy a high average humidity of 86% that adds to the lush ambiance of the area.

December Temperature in Santa Rosa

In December in Santa Rosa, the average temperature is 18°C (65°F). Maximums can reach 34°C (93°F), and minimums can drop as low as 1°C (33°F). This range makes it essential for travelers to pack both light clothing for warmer days and layering options for cooler evenings.

December Weather in Santa Rosa: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Santa Rosa, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Santa Rosa, December typically has an average temperature of 18°C (65°F), with highs reaching up to 34°C (93°F) and lows dropping to around 1°C (33°F).
JanFebMarAprMayJunJulAugSepOctNovDec626572768284868783776964
Data source: Temperature data for Santa Rosa generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Santa Rosa

In Santa Rosa in December, the total precipitation amount is 23 mm (0.9 in) over a span of 4 days.

December Precipitation Trends in Santa Rosa

The chart displays monthly precipitation patterns in Santa Rosa, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Santa Rosa, December typically receives around 23 mm (0.9 inches) of precipitation spread over approximately 4 days.
JanFebMarAprMayJunJulAugSepOctNovDec2421353081919433114653023
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

December Humidity in Santa Rosa

In Santa Rosa in December humidity is 86%. With an average temperature of 18°C (65°F), this humidity feels like you’re wrapped in a warm, heavy blanket, making outdoor activities feel quite muggy and sticky for traveling.

December Average Humidity in Santa Rosa

This chart illustrates the average monthly humidity levels in Santa Rosa, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Santa Rosa is approximately 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec83%79%76%77%80%73%66%65%73%76%80%86%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Santa Rosa

In Santa Rosa in December, the maximum UV index is 6, which corresponds to a high Exposure Category. The time to burn is approximately 25 minutes. To find the hourly UV index in Santa Rosa, you can refer to this Hourly UV Index in Santa Rosa.

Maximum UV Index Levels in Santa Rosa for December

The chart shows the monthly maximum UV Index (UVI) for Santa Rosa in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Santa Rosa typically reaches 6, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec69101112121212111076
Data source: Santa Rosa December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How December Weather in Santa Rosa Compares to Other Months

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.

This table compares monthly weather conditions in Santa Rosa, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather17°C (62°F)24 mm (1.0 inches)83%high
February Weather18°C (65°F)21 mm (0.8 inches)79%very high
March Weather22°C (72°F)35 mm (1.4 inches)76%very high
April Weather25°C (77°F)30 mm (1.2 inches)77%extreme
May Weather28°C (82°F)81 mm (3.2 inches)80%extreme
June Weather29°C (85°F)91 mm (3.6 inches)73%extreme
July Weather30°C (86°F)94 mm (3.7 inches)66%extreme
August Weather30°C (87°F)33 mm (1.3 inches)65%extreme
September Weather28°C (83°F)114 mm (4.5 inches)73%extreme
October Weather25°C (77°F)64 mm (2.5 inches)76%very high
November Weather21°C (69°F)30 mm (1.2 inches)80%high
December Weather18°C (65°F)23 mm (0.9 inches)86%high

Compare Santa Rosa's Climate with Cities Worldwide