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December Weather in Riverside, United States

Last updated: June 24, 2025

In December, the average temperature in Riverside, United States hovers around -2°C (29°F), making it a truly chilly time of year. Be prepared for minimum temperatures dipping to -14°C (8°F) and the occasional highs reaching up to 13°C (56°F). The weather is also quite damp, with about 33 mm (1.3 in) of precipitation over 9 days, contributing to an average humidity of 87%. Bundle up and stay warm!

December Temperature in Riverside

In December in Riverside, the average temperature is -2°C (29°F), with maximums reaching 13°C (56°F) and minimums dropping as low as -14°C (8°F). Be prepared for chilly weather and pack accordingly if you plan to visit during this time.

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

The chart illustrates December temperature patterns in Riverside, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Riverside, December typically has an average temperature of -2°C (29°F), with highs reaching up to 13°C (56°F) and lows dropping to around -14°C (8°F).
JanFebMarAprMayJunJulAugSepOctNovDec273041485769787464473829
Data source: Temperature data for Riverside 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 Riverside

In Riverside in December, the precipitation amount is 33 mm (1.3 in) over the course of 9 days.

December Precipitation Trends in Riverside

The chart displays monthly precipitation patterns in Riverside, 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 Riverside, December typically receives around 33 mm (1.3 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec32404037432071120292233
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Riverside

In Riverside in December humidity is 87%. With an average temperature of -2°C (29°F), this humidity feels like an uncomfortable chill that seeps into your bones, making it challenging to enjoy outdoor activities.

December Average Humidity in Riverside

This chart illustrates the average monthly humidity levels in Riverside, 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 Riverside is approximately 87%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%92%85%76%66%62%53%42%46%64%83%87%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Riverside

In Riverside 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 Riverside, you can check the information here.

Maximum UV Index Levels in Riverside for December

The chart shows the monthly maximum UV Index (UVI) for Riverside 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 Riverside typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3578101111109643
Data source: Riverside 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 Riverside Compares to Other Months

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

This table compares monthly weather conditions in Riverside, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-3°C (27°F)32 mm (1.3 inches)91%moderate
February Weather-1°C (31°F)40 mm (1.6 inches)92%moderate
March Weather5°C (41°F)40 mm (1.6 inches)85%high
April Weather9°C (48°F)37 mm (1.4 inches)76%very high
May Weather14°C (58°F)43 mm (1.7 inches)66%very high
June Weather20°C (69°F)20 mm (0.8 inches)62%extreme
July Weather25°C (78°F)7 mm (0.3 inches)53%extreme
August Weather24°C (75°F)11 mm (0.4 inches)42%very high
September Weather18°C (64°F)20 mm (0.8 inches)46%very high
October Weather8°C (48°F)29 mm (1.1 inches)64%high
November Weather3°C (38°F)22 mm (0.9 inches)83%moderate
December Weather-2°C (29°F)33 mm (1.3 inches)87%moderate

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