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December Weather in Merrillan, United States

Last updated: June 24, 2025

In Merrillan, United States, the average temperature in December hovers around -4°C (25°F). During this time, temperatures can drop as low as -31°C (-23°F) or rise to a maximum of 16°C (61°F). Expect about 50 mm (2.0 in) of precipitation spread over 8 days, and prepare for fairly high humidity with an average of 85%.

December Temperature in Merrillan

In December in Merrillan, the average temperature is -4°C (25°F). The maximum can reach 16°C (61°F), while the minimum can drop as low as -31°C (-23°F). Be prepared for a wide range of temperatures if you plan to travel during this time.

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

The chart illustrates December temperature patterns in Merrillan, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Merrillan, December typically has an average temperature of -4°C (25°F), with highs reaching up to 16°C (61°F) and lows dropping to around -31°C (-23°F).
JanFebMarAprMayJunJulAugSepOctNovDec181934445869726963483425
Data source: Temperature data for Merrillan 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 Merrillan

In Merrillan in December, the total precipitation amount is 50 mm (2.0 in) spread over 8 days.

December Precipitation Trends in Merrillan

The chart displays monthly precipitation patterns in Merrillan, 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 Merrillan, December typically receives around 50 mm (2.0 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec33525695130135112136971195350
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Merrillan

In Merrillan in December, humidity is 85%. With an average temperature of -4°C (25°F), this humidity feels like a damp chill clinging to your skin, making travel outside uncomfortable and leaving you feeling cold and clammy despite the freezing temperatures.

December Average Humidity in Merrillan

This chart illustrates the average monthly humidity levels in Merrillan, 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 Merrillan is approximately 85%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%89%86%85%79%80%80%78%80%84%89%85%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Merrillan

In Merrillan in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Merrillan, you can visit Hourly UV Index in Merrillan.

Maximum UV Index Levels in Merrillan for December

The chart shows the monthly maximum UV Index (UVI) for Merrillan 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 Merrillan typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec24588101097532
Data source: Merrillan 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 Merrillan Compares to Other Months

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

This table compares monthly weather conditions in Merrillan, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-8°C (18°F)33 mm (1.3 inches)88%low
February Weather-7°C (19°F)52 mm (2.1 inches)89%moderate
March Weather1°C (34°F)56 mm (2.2 inches)86%moderate
April Weather6°C (44°F)95 mm (3.8 inches)85%very high
May Weather15°C (58°F)130 mm (5.1 inches)79%very high
June Weather20°C (69°F)135 mm (5.3 inches)80%very high
July Weather22°C (73°F)112 mm (4.4 inches)80%very high
August Weather20°C (69°F)136 mm (5.4 inches)78%very high
September Weather17°C (63°F)97 mm (3.8 inches)80%high
October Weather9°C (49°F)119 mm (4.7 inches)84%moderate
November Weather1°C (34°F)53 mm (2.1 inches)89%moderate
December Weather-4°C (25°F)50 mm (2.0 inches)85%low

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