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August Weather in Portola Valley, United States

Last updated: June 24, 2025

In August, the average temperature in Portola Valley, United States is a pleasant 18°C (65°F). Expect some variability, with minimum temperatures dropping to 12°C (54°F) and maximums soaring to 35°C (96°F). Enjoy clear skies, as precipitation is a mere 0 mm (0.0 in) over the entire month, and the average humidity remains comfortable at 54%.

August Temperature in Portola Valley

In August in Portola Valley, the average temperature is 18°C (65°F). Maximum temperatures can reach 35°C (96°F), while minimums can drop to 12°C (54°F). Overall, it's a great time to visit for those who enjoy mild weather with warm days and cooler evenings.

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

The chart illustrates August 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, August typically has an average temperature of 18°C (65°F), with highs reaching up to 35°C (96°F) and lows dropping to around 12°C (54°F).
JanFebMarAprMayJunJulAugSepOctNovDec525354565863636565625652
Data source: Temperature data for Portola Valley generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

August Precipitation in Portola Valley

In Portola Valley in August, the precipitation amount is 0 mm (0.0 in) during 0 days.

August Precipitation Trends in Portola Valley

The chart displays monthly precipitation patterns in Portola Valley, with values for each month alongside August’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how August’s conditions compare to those of other months. In Portola Valley, August typically receives around 0 mm (0.0 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec1051008633242012244788
Data source: Precipitation data for August generated using information from the Copernicus Climate Change Service.
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August Humidity in Portola Valley

In Portola Valley in August, humidity is 54%. With an average temperature of 18°C (65°F), this humidity feels like a light, refreshing breeze, making it comfortable for traveling and exploring the area without the discomfort of excessive stickiness.

August Average Humidity in Portola Valley

This chart illustrates the average monthly humidity levels in Portola Valley, with August’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In August, average humidity in Portola Valley is approximately 54%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%84%82%78%71%64%59%54%55%62%78%80%
Data source: Humidity data for August generated using information from the Copernicus Climate Change Service.

August UV Index in Portola Valley

In Portola Valley in August, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Portola Valley.

Maximum UV Index Levels in Portola Valley for August

The chart shows the monthly maximum UV Index (UVI) for Portola Valley in August, 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 August, the maximum UV index in Portola Valley typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109743
Data source: Portola Valley August 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 August 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 August’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 August’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather11°C (52°F)105 mm (4.1 inches)82%moderate
February Weather11°C (53°F)100 mm (3.9 inches)84%moderate
March Weather12°C (54°F)86 mm (3.4 inches)82%very high
April Weather13°C (57°F)33 mm (1.3 inches)78%very high
May Weather15°C (59°F)24 mm (0.9 inches)71%very high
June Weather17°C (63°F)2 mm (0.1 inches)64%extreme
July Weather17°C (63°F)0 mm (0.0 inches)58%extreme
August Weather18°C (65°F)0 mm (0.0 inches)54%very high
September Weather18°C (66°F)2 mm (0.1 inches)55%very high
October Weather17°C (63°F)24 mm (0.9 inches)62%high
November Weather13°C (56°F)47 mm (1.9 inches)78%moderate
December Weather11°C (52°F)88 mm (3.5 inches)80%moderate

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