January Weather in Portola Valley, United States

Last updated: June 24, 2025

In January, the average temperature in Portola Valley, United States is a comfortable 11°C (52°F). Expect a range from a chilly minimum of 2°C (36°F) to a warm maximum of 24°C (75°F). Prepare for some rain, as the average precipitation reaches 105 mm (4.1 in) over about 7 days, coupled with a high average humidity of 82%.

January Temperature in Portola Valley

In January in Portola Valley, the average temperature is 11°C (52°F). Maximum temperatures can reach 24°C (75°F), while minimum temperatures can drop as low as 2°C (36°F). It's a great time to visit for those who enjoy mild weather and comfortable temperatures.

January Weather in Portola Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates January temperature patterns in Portola Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Portola Valley, January typically has an average temperature of 11°C (52°F), with highs reaching up to 24°C (75°F) and lows dropping to around 2°C (36°F).

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

January Precipitation in Portola Valley

In Portola Valley in January, the precipitation amount is 105 mm (4.1 in) over a period of 7 days.

January Precipitation Trends in Portola Valley

The chart displays monthly precipitation patterns in Portola Valley, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In Portola Valley, January typically receives around 105 mm (4.1 inches) of precipitation spread over approximately 7 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

January Humidity in Portola Valley

In Portola Valley in January, humidity is 82%. With an average temperature of 11°C (52°F), this humidity feels like a damp chill that seeps into your bones, making it essential to dress in layers and stay prepared for the moisture-laden air as you explore your surroundings.

January Average Humidity in Portola Valley

This chart illustrates the average monthly humidity levels in Portola Valley, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in Portola Valley is approximately 82%, offering insight into how humid the weather typically is during this month.

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

January UV Index in Portola Valley

In Portola Valley in January, 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 Valley, you can check the information here.

Maximum UV Index Levels in Portola Valley for January

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

Data source: Portola Valley January 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 January Weather in Portola Valley Compares to Other Months

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

This table compares monthly weather conditions in Portola Valley, showing how January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	11°C (52°F)	105 mm (4.1 inches)	82%	moderate
February Weather	11°C (53°F)	100 mm (3.9 inches)	84%	moderate
March Weather	12°C (54°F)	86 mm (3.4 inches)	82%	very high
April Weather	13°C (57°F)	33 mm (1.3 inches)	78%	very high
May Weather	15°C (59°F)	24 mm (0.9 inches)	71%	very high
June Weather	17°C (63°F)	2 mm (0.1 inches)	64%	extreme
July Weather	17°C (63°F)	0 mm (0.0 inches)	58%	extreme
August Weather	18°C (65°F)	0 mm (0.0 inches)	54%	very high
September Weather	18°C (66°F)	2 mm (0.1 inches)	55%	very high
October Weather	17°C (63°F)	24 mm (0.9 inches)	62%	high
November Weather	13°C (56°F)	47 mm (1.9 inches)	78%	moderate
December Weather	11°C (52°F)	88 mm (3.5 inches)	80%	moderate