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December Weather in California, United States

Last updated: June 24, 2025

In California, United States, the average temperature in December hovers around 4°C (39°F). Temperatures can swing from a chilly -16°C (3°F) at their lowest to a warm 25°C (76°F) at their highest. During this month, expect about 38 mm (1.5 in) of precipitation spread over 5 days, along with an average humidity of 86%.

December Temperature in California

In December in California, the average temperature is 4°C (39°F). The maximum can reach 25°C (76°F), while the minimum can drop to as low as -16°C (3°F). Be prepared for a wide range of temperatures if you're planning to travel during this time.

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

The chart illustrates December temperature patterns in California, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In California, December typically has an average temperature of 4°C (39°F), with highs reaching up to 25°C (76°F) and lows dropping to around -16°C (3°F).
JanFebMarAprMayJunJulAugSepOctNovDec323547546676807672584539
Data source: Temperature data for California 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 California

In California in December, the total precipitation amount is 38 mm (1.5 in) spread over a duration of 5 days.

December Precipitation Trends in California

The chart displays monthly precipitation patterns in California, 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 California, December typically receives around 38 mm (1.5 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec6860114124176113115106611075638
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in California

In California in December humidity is 86%. With an average temperature of 4°C (39°F), this humidity feels like a chilly mist enveloping you, making it essential to bundle up while exploring, as each breath comes with a damp chill that can be quite refreshing yet starkly invigorating for travelers.

December Average Humidity in California

This chart illustrates the average monthly humidity levels in California, 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 California is approximately 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%78%75%77%82%83%81%78%72%72%84%86%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in California

In California 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 California, you can check the information here.

Maximum UV Index Levels in California for December

The chart shows the monthly maximum UV Index (UVI) for California 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 California typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579101111109743
Data source: California 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 California Compares to Other Months

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

This table compares monthly weather conditions in California, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (33°F)68 mm (2.7 inches)80%moderate
February Weather1°C (35°F)60 mm (2.4 inches)78%moderate
March Weather8°C (47°F)114 mm (4.5 inches)75%high
April Weather12°C (55°F)124 mm (4.9 inches)77%very high
May Weather19°C (67°F)175 mm (6.9 inches)82%very high
June Weather25°C (77°F)113 mm (4.4 inches)83%extreme
July Weather26°C (80°F)115 mm (4.5 inches)81%extreme
August Weather25°C (77°F)106 mm (4.2 inches)78%very high
September Weather22°C (73°F)61 mm (2.4 inches)72%very high
October Weather14°C (58°F)107 mm (4.2 inches)72%high
November Weather7°C (45°F)56 mm (2.2 inches)84%moderate
December Weather4°C (39°F)38 mm (1.5 inches)86%moderate

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