December Weather in Portola, United States

Last updated: June 24, 2025

In Portola, United States, the average temperature in December hovers around -2°C (29°F). This chilly month can see drastic fluctuations, with minimums dropping to -17°C (1°F) and maximums reaching up to 14°C (58°F). Expect a fair share of precipitation, totaling around 132 mm (5.2 in) over approximately 10 days. Humidity remains high at an average of 83%, adding to the crisp atmosphere.

December Temperature in Portola

In December in Portola, the average temperature is -2°C (29°F), with a maximum of 14°C (58°F) and a minimum that can plummet to -17°C (1°F). Be prepared for a chilly adventure, but don't forget to enjoy the breathtaking winter scenery!

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

The chart illustrates December temperature patterns in Portola, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Portola, December typically has an average temperature of -2°C (29°F), with highs reaching up to 14°C (58°F) and lows dropping to around -17°C (1°F).

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

December Precipitation in Portola

In Portola in December, the total precipitation amount is 132 mm (5.2 in) over a span of 10 days.

December Precipitation Trends in Portola

The chart displays monthly precipitation patterns in Portola, 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 Portola, December typically receives around 132 mm (5.2 inches) of precipitation spread over approximately 10 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 Portola

In Portola in December, humidity is 83%. With an average temperature of -2°C (29°F), this humidity feels like a biting chill that seeps into your bones, making travel outside feel particularly uncomfortable and brisk, as the damp air enhances the cold sensation, leaving you longing for warmth and shelter.

December Average Humidity in Portola

This chart illustrates the average monthly humidity levels in Portola, 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 Portola is approximately 83%, 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 Portola

In Portola 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 Portola, you can check the information here.

Maximum UV Index Levels in Portola for December

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

Data source: Portola 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 Portola Compares to Other Months

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

This table compares monthly weather conditions in Portola, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-1°C (31°F)	170 mm (6.7 inches)	84%	moderate
February Weather	-1°C (30°F)	177 mm (7.0 inches)	84%	high
March Weather	1°C (34°F)	146 mm (5.7 inches)	83%	very high
April Weather	5°C (41°F)	72 mm (2.8 inches)	81%	very high
May Weather	10°C (51°F)	60 mm (2.3 inches)	74%	extreme
June Weather	16°C (62°F)	10 mm (0.4 inches)	64%	extreme
July Weather	21°C (70°F)	10 mm (0.4 inches)	44%	extreme
August Weather	20°C (68°F)	13 mm (0.5 inches)	36%	extreme
September Weather	15°C (60°F)	19 mm (0.7 inches)	44%	very high
October Weather	8°C (47°F)	43 mm (1.7 inches)	65%	high
November Weather	3°C (38°F)	79 mm (3.1 inches)	84%	moderate
December Weather	-2°C (29°F)	132 mm (5.2 inches)	83%	moderate