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December Weather in San Mateo, United States

Last updated: June 24, 2025

In December, the average temperature in San Mateo, United States hovers around 11°C (52°F). Expect a minimum chill of 3°C (37°F) and a pleasant maximum of 22°C (72°F). This month typically brings 88 mm (3.5 in) of precipitation spread over about 9 days, contributing to an average humidity of 80%. Perfect for cozy indoor activities or exploring the lush, vibrant surroundings!

December Temperature in San Mateo

In December in San Mateo, the average temperature is 11°C (52°F). Maximums can reach 22°C (72°F), while minimums can be as low as 3°C (37°F). This mild weather makes San Mateo an ideal destination for outdoor exploration and sightseeing.

December Weather in San Mateo: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in San Mateo, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Mateo, December typically has an average temperature of 11°C (52°F), with highs reaching up to 22°C (72°F) and lows dropping to around 3°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec525354565863636565625652
Data source: Temperature data for San Mateo 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 San Mateo

In San Mateo in December, the precipitation amount is 88 mm (3.5 in) over the course of 9 days.

December Precipitation Trends in San Mateo

The chart displays monthly precipitation patterns in San Mateo, 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 San Mateo, December typically receives around 88 mm (3.5 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec1051008633242012244788
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in San Mateo

In San Mateo in December, humidity is 80%. With an average temperature of 11°C (52°F), this humidity feels like a damp blanket wrapping around you, making travel a bit uncomfortable as you navigate through the thick, languid air.

December Average Humidity in San Mateo

This chart illustrates the average monthly humidity levels in San Mateo, 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 San Mateo is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%84%82%78%71%64%59%54%55%62%78%80%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in San Mateo

In San Mateo 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 San Mateo, you can check the information here.

Maximum UV Index Levels in San Mateo for December

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

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

This table compares monthly weather conditions in San Mateo, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather11°C (52°F)105 mm (4.1 inches)82%moderate
February Weather11°C (53°F)100 mm (3.9 inches)84%moderate
March Weather12°C (54°F)86 mm (3.4 inches)82%very high
April Weather13°C (57°F)33 mm (1.3 inches)78%very high
May Weather15°C (59°F)24 mm (0.9 inches)71%very high
June Weather17°C (63°F)2 mm (0.1 inches)64%extreme
July Weather17°C (63°F)0 mm (0.0 inches)58%extreme
August Weather18°C (65°F)0 mm (0.0 inches)54%very high
September Weather18°C (66°F)2 mm (0.1 inches)55%very high
October Weather17°C (63°F)24 mm (0.9 inches)62%high
November Weather13°C (56°F)47 mm (1.9 inches)78%moderate
December Weather11°C (52°F)88 mm (3.5 inches)80%moderate

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