December Weather in Upland, United States

Last updated: June 24, 2025

In December, the average temperature in Upland, United States is a crisp 4°C (40°F). Visitors can expect a chilly minimum of -11°C (13°F), while the mercury may reach as high as 19°C (66°F). Precipitation is moderate, with about 100 mm (3.9 in) spread over 9 days, alongside a notable average humidity of 84%.

December Temperature in Upland

In December in Upland, the average temperature is 4°C (40°F). The maximum can reach 19°C (66°F), and the minimum can be as low as -11°C (13°F). Travelers should be prepared for a wide range of temperatures, so dressing in layers is advisable.

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

The chart illustrates December temperature patterns in Upland, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Upland, December typically has an average temperature of 4°C (40°F), with highs reaching up to 19°C (66°F) and lows dropping to around -11°C (13°F).

Data source: Temperature data for Upland generated using information from the Copernicus Climate Change Service.

December Precipitation in Upland

In Upland in December, the precipitation amount is 100 mm (3.9 in) spread over 9 days.

December Precipitation Trends in Upland

The chart displays monthly precipitation patterns in Upland, 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 Upland, December typically receives around 100 mm (3.9 inches) of precipitation spread over approximately 9 days.

Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

December Humidity in Upland

In Upland in December, humidity is 84%. With an average temperature of 4°C (40°F), this humidity feels like a damp chill that seeps into your bones, making outdoor activities uncomfortable and requiring extra layers to stay warm and dry while traveling.

December Average Humidity in Upland

This chart illustrates the average monthly humidity levels in Upland, 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 Upland is approximately 84%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Upland

In Upland 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 Upland, you can check the information here.

Maximum UV Index Levels in Upland for December

The chart shows the monthly maximum UV Index (UVI) for Upland 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 Upland typically reaches 3, which falls under the moderate exposure category.

Data source: Upland 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 Upland Compares to Other Months

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

This table compares monthly weather conditions in Upland, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	2°C (36°F)	64 mm (2.5 inches)	84%	moderate
February Weather	4°C (39°F)	103 mm (4.1 inches)	83%	moderate
March Weather	7°C (45°F)	106 mm (4.2 inches)	83%	high
April Weather	13°C (55°F)	105 mm (4.1 inches)	81%	very high
May Weather	18°C (65°F)	135 mm (5.3 inches)	78%	very high
June Weather	23°C (74°F)	118 mm (4.7 inches)	79%	very high
July Weather	26°C (79°F)	136 mm (5.4 inches)	74%	very high
August Weather	25°C (77°F)	140 mm (5.5 inches)	72%	very high
September Weather	22°C (71°F)	100 mm (3.9 inches)	75%	very high
October Weather	16°C (61°F)	109 mm (4.3 inches)	81%	high
November Weather	8°C (47°F)	83 mm (3.3 inches)	85%	moderate
December Weather	4°C (40°F)	100 mm (3.9 inches)	84%	moderate