December Weather in Portola Valley

Last updated: March 2, 2024

The weather in Portola Valley, United States, during December is characterized by an average temperature of 11°C (52°F). Highs can soar to 19°C (67°F), while lows may dip to 4°C (39°F). Typically, the humidity level in Portola Valley throughout December hovers around 80%.

4°C (39°F)

Minimum temperature

11°C (52°F)

Average temperature

19°C (67°F)

Maximum temperature

80%

Humidity

Precipitation and Sunshine hours

In December, Portola Valley averages 88 mm (3.5 inches) of rainfall, typically over the course of 9 rainy days. The month enjoys an average of 9 hours 36 minutes of daylight, with the sun shining for approximately 6 hours 16 minutes each day. Additionally, there is a 35% probability of sunny days during this period.

88 mm (3.5 inches)

Precipitation

9 rainy days

Rainy days

6 hours 16 minutes

Sunshine hours

35%

Chance of sun

UV Index

In December, the UV Index in Portola Valley reaches a maximum of 3, indicating a level of Moderate exposure. The most intense UV radiation typically occurs between 11:00 and 13:00, during which unprotected skin may burn in as little as 30 minutes.

Average solar exposure data for the current time of the year. Actual values may vary and depend on many factors, such as cloud cover, vegetation cover, surface type, etc.
  07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00
UVI 0 1 1 2 3 3 3 2 1 1 0 0 0
Exposure Low Moderate Low
Time to burn 45 min 30 min 45 min

Compare Portola Valley's Climate with Cities Worldwide