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December Weather in Santa Rosa, United States

Last updated: June 24, 2025

In December, the average temperature in Santa Rosa, United States hovers around 9°C (48°F). Expect a chilly minimum of -2°C (29°F) and a warm maximum reaching up to 23°C (73°F). During this time, you can anticipate approximately 101 mm (4.0 in) of precipitation over 8 days, with an average humidity level of 84%, making for a rather damp atmosphere.

December Temperature in Santa Rosa

In December in Santa Rosa, the average temperature is 9°C (48°F). Maximums can reach 23°C (73°F) and minimums can be as low as -2°C (29°F). Be prepared for a diverse range of temperatures and pack accordingly for your travels!

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 9°C (48°F), with highs reaching up to 23°C (73°F) and lows dropping to around -2°C (29°F).
JanFebMarAprMayJunJulAugSepOctNovDec485052576269717169635348
Data source: Temperature data for Santa Rosa generated using information from the Copernicus Climate Change Service.
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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 precipitation amount is 101 mm (4.0 in) spread over 8 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 101 mm (4.0 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec13915597452820024158101
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Santa Rosa

In Santa Rosa in December, humidity is 84%. With an average temperature of 9°C (48°F), this humidity feels like a damp chill that envelops you, making it essential to dress in layers and stay active, as the moisture in the air can quickly lead to discomfort while 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 84%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%83%80%80%76%70%66%68%72%84%84%
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 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Santa Rosa, you can check the information here.

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 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579101111109643
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 Weather9°C (49°F)139 mm (5.5 inches)86%moderate
February Weather10°C (50°F)155 mm (6.1 inches)84%moderate
March Weather11°C (52°F)97 mm (3.8 inches)83%high
April Weather14°C (57°F)45 mm (1.8 inches)80%very high
May Weather17°C (62°F)27 mm (1.1 inches)80%very high
June Weather21°C (69°F)2 mm (0.1 inches)76%extreme
July Weather22°C (71°F)0 mm (0.0 inches)70%extreme
August Weather21°C (71°F)0 mm (0.0 inches)66%very high
September Weather20°C (69°F)2 mm (0.1 inches)68%very high
October Weather17°C (63°F)41 mm (1.6 inches)72%high
November Weather12°C (54°F)58 mm (2.3 inches)84%moderate
December Weather9°C (48°F)101 mm (4.0 inches)84%moderate

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