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December Weather in Millbrae, United States

Last updated: June 24, 2025

In December, the average temperature in Millbrae, United States hovers around 12°C (53°F), offering a refreshing climate. Expect minimum temperatures to dip to 6°C (44°F), while it can reach a pleasant maximum of 19°C (67°F). With about 92 mm (3.6 in) of precipitation spread over 10 days, it's wise to carry an umbrella. Moreover, the average humidity stands at a comfortable 79%, making it a lovely time to experience this destination!

December Temperature in Millbrae

In December in Millbrae, the average temperature is 12°C (53°F), with maximums reaching 19°C (67°F) and minimums dropping as low as 6°C (44°F). This mild weather makes it a perfect time for outdoor activities and exploring the local attractions.

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

The chart illustrates December temperature patterns in Millbrae, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Millbrae, December typically has an average temperature of 12°C (53°F), with highs reaching up to 19°C (67°F) and lows dropping to around 6°C (44°F).
JanFebMarAprMayJunJulAugSepOctNovDec525253545558586062595653
Data source: Temperature data for Millbrae 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 Millbrae

In Millbrae in December, the total precipitation amount is 92 mm (3.6 in), which falls over the course of 10 days.

December Precipitation Trends in Millbrae

The chart displays monthly precipitation patterns in Millbrae, 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 Millbrae, December typically receives around 92 mm (3.6 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec1021017834224333274892
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Millbrae

In Millbrae in December, humidity is 79%. With an average temperature of 12°C (53°F), this humidity feels like a damp blanket enveloping you, making outdoor activities slightly uncomfortable and ideal for cozy indoor explorations rather than extensive sightseeing.

December Average Humidity in Millbrae

This chart illustrates the average monthly humidity levels in Millbrae, 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 Millbrae is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%82%82%79%83%84%87%87%86%80%79%79%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Millbrae

In Millbrae 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 Millbrae, you can check the information here.

Maximum UV Index Levels in Millbrae for December

The chart shows the monthly maximum UV Index (UVI) for Millbrae 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 Millbrae typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109743
Data source: Millbrae 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 Millbrae Compares to Other Months

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

This table compares monthly weather conditions in Millbrae, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather11°C (53°F)102 mm (4.0 inches)85%moderate
February Weather11°C (53°F)101 mm (4.0 inches)82%moderate
March Weather12°C (53°F)77 mm (3.0 inches)82%very high
April Weather12°C (55°F)34 mm (1.3 inches)79%very high
May Weather13°C (56°F)22 mm (0.9 inches)83%very high
June Weather15°C (58°F)4 mm (0.2 inches)84%extreme
July Weather15°C (59°F)3 mm (0.1 inches)87%extreme
August Weather16°C (61°F)3 mm (0.1 inches)87%very high
September Weather16°C (62°F)3 mm (0.1 inches)86%very high
October Weather15°C (60°F)27 mm (1.1 inches)80%high
November Weather13°C (56°F)48 mm (1.9 inches)79%moderate
December Weather12°C (53°F)92 mm (3.6 inches)79%moderate

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