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December Weather in Petaluma, United States

Last updated: June 24, 2025

In December, the average temperature in Petaluma, United States hovers around 9°C (49°F). Visitors can expect a minimum of 0°C (33°F) and a maximum of 22°C (72°F). With an average precipitation of 103 mm (4.1 in) spread over 9 days, and an average humidity level of 84%, it's wise to prepare for a mix of chilly and damp weather.

December Temperature in Petaluma

In December in Petaluma, the average temperature is 9°C (49°F). Maximum temperatures can reach up to 22°C (72°F), while minimums can drop as low as 0°C (33°F). Be sure to pack layers to accommodate both warm days and chilly nights during your travels!

December Weather in Petaluma: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Petaluma, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Petaluma, December typically has an average temperature of 9°C (49°F), with highs reaching up to 22°C (72°F) and lows dropping to around 0°C (33°F).
JanFebMarAprMayJunJulAugSepOctNovDec505152565964656565615449
Data source: Temperature data for Petaluma 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 Petaluma

In Petaluma in December, the precipitation amount is 103 mm (4.1 in) distributed over 9 days.

December Precipitation Trends in Petaluma

The chart displays monthly precipitation patterns in Petaluma, 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 Petaluma, December typically receives around 103 mm (4.1 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec13114793452721123859103
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Petaluma

In Petaluma in December, humidity is 84%. With an average temperature of 9°C (49°F), this humidity feels like a chilly embrace, making travel uncomfortable as the dampness seeps into your clothes and lingers in the air, leaving you feeling cool yet clammy.

December Average Humidity in Petaluma

This chart illustrates the average monthly humidity levels in Petaluma, 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 Petaluma 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 Petaluma

In Petaluma 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 Petaluma, you can check the information here.

Maximum UV Index Levels in Petaluma for December

The chart shows the monthly maximum UV Index (UVI) for Petaluma 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 Petaluma typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579101111109643
Data source: Petaluma 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 Petaluma Compares to Other Months

Weather in Petaluma varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Petaluma, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Petaluma, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (50°F)131 mm (5.2 inches)86%moderate
February Weather10°C (51°F)147 mm (5.8 inches)84%moderate
March Weather11°C (52°F)93 mm (3.7 inches)83%high
April Weather13°C (56°F)45 mm (1.8 inches)80%very high
May Weather15°C (60°F)27 mm (1.0 inches)80%very high
June Weather18°C (65°F)2 mm (0.1 inches)76%extreme
July Weather18°C (65°F)1 mm (0.0 inches)70%extreme
August Weather18°C (65°F)1 mm (0.0 inches)66%very high
September Weather18°C (65°F)2 mm (0.1 inches)68%very high
October Weather16°C (61°F)38 mm (1.5 inches)72%high
November Weather12°C (54°F)59 mm (2.3 inches)84%moderate
December Weather9°C (49°F)103 mm (4.1 inches)84%moderate

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