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%.
Minimum temperature
Average temperature
Maximum temperature
Humidity
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.
Precipitation
Rainy days
Sunshine hours
Chance of sun
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.
| 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 | ||||||||||