Monthly weather forecast and climate
Portola Valley, CA

Weather in January

January, like December, is another mild winter month in Portola Valley, California, with temperature in the range of an average low of 46.4°F (8°C) and an average high of 56.7°F (13.7°C). In January, the average high-temperature is almost the same as in December - a still mild 56.7°F (13.7°C). Weather in January »

Weather in February

February, the last month of the winter, in Portola Valley, is another mild month, with average temperature fluctuating between 46.4°F (8°C) and 58.3°F (14.6°C). In Portola Valley, the average high-temperature is practically the same as in January - a still moderate 58.3°F (14.6°C). Weather in February »

Weather in March

March, the first month of the spring, in Portola Valley, is still a mild month, with average temperature ranging between min 46.9°F (8.3°C) and max 59.5°F (15.3°C). In Portola Valley, the average high-temperature in March is practically the same as in February - a still mild 59.5°F (15.3°C). Weather in March »

Weather in April

April is an enjoyable spring month in Portola Valley, California, with average temperature varying between 62.2°F (16.8°C) and 48.2°F (9°C). In Portola Valley, the average high-temperature is practically the same as in March - a comfortable 62.2°F (16.8°C). Weather in April »

Weather in May

May, the last month of the spring, in Portola Valley, is another comfortable month, with average temperature varying between 50.2°F (10.1°C) and 64.9°F (18.3°C). In Portola Valley, the average high-temperature in May is practically the same as in April - a still enjoyable 64.9°F (18.3°C). Weather in May »

Weather in June

The first month of the summer, June, is an agreeable month in Portola Valley, California, with temperature in the range of an average high of 70°F (21.1°C) and an average low of 53.4°F (11.9°C). In Portola Valley, California, the average high-temperature in June is practically the same as in May - an agreeable 70°F (21.1°C). Weather in June »

Weather in July

July, like June, is an agreeable summer month in Portola Valley, California, with temperature in the range of an average high of 72.7°F (22.6°C) and an average low of 54.7°F (12.6°C). In July, the average high-temperature is practically the same as in June - a still agreeable 72.7°F (22.6°C). Weather in July »

Weather in August

The last month of the summer, August, is another pleasant month in Portola Valley, California, with average temperature ranging between max 73°F (22.8°C) and min 56.7°F (13.7°C). With an average high-temperature of 73°F (22.8°C) and an average low-temperature of 56.7°F (13.7°C), August is the warmest month. Weather in August »

Weather in September

The first month of the autumn, September, is also an agreeable month in Portola Valley, California, with temperature in the range of an average low of 56.7°F (13.7°C) and an average high of 72.5°F (22.5°C). In Portola Valley, the average high-temperature is almost the same as in August - a still agreeable 72.5°F (22.5°C). Weather in September »

Weather in October

October, the same as September, in Portola Valley, California, is another pleasant autumn month, with temperature in the range of an average low of 54.9°F (12.7°C) and an average high of 68.2°F (20.1°C). In October, the average high-temperature is practically the same as in September - a still agreeable 68.2°F (20.1°C). Weather in October »

Weather in November

The last month of the autumn, November, is also an enjoyable month in Portola Valley, California, with average temperature varying between 61.9°F (16.6°C) and 50.5°F (10.3°C). In November, the average high-temperature slightly decreases, from a pleasant 68.2°F (20.1°C) in October, to a comfortable 61.9°F (16.6°C). Weather in November »

Weather in December

The first month of the winter, December, is also a moderate month in Portola Valley, California, with temperature in the range of an average high of 55.8°F (13.2°C) and an average low of 47.1°F (8.4°C). The coldest month is December, with an average high-temperature of 55.8°F (13.2°C) and an average low-temperature of 47.1°F (8.4°C). Weather in December »
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FAQ

How many days does it rain in Portola Valley?

In Portola Valley, during the entire year, the rain falls for 57.5 days and collects up to 4.76" (121mm) of precipitation.

What is the wettest month in Portola Valley?

The month with the most rainfall is February when the rain falls for 6.6 days and typically aggregates up to 0.98" (25mm) of precipitation.

What are the months with the lowest UV index in Portola Valley?

February, November and December, with an average maximum UV index of 3, are months with the lowest UV index in Portola Valley, California.

What is the most humid month in Portola Valley?

With an average relative humidity of 76%, March is the most humid month in Portola Valley.

What is the driest month in Portola Valley?

June is the month with the least rainfall in Portola Valley, California. Rain falls for 0.9 days and accumulates 0.04" (1mm) of precipitation.

When are the longest days in Portola Valley?

With an average of 14.7h of daylight, June has the longest days of the year.

What are the months with the highest UV index in Portola Valley?

Months with the highest UV index are June through September, with an average maximum UV index of 5.

What month has the most sunshine in Portola Valley?

With an average of 12h of sunshine, July has the most sunshine of the year in Portola Valley.

What is the warmest month in Portola Valley?

The warmest month in Portola Valley, California, is August, with an average high-temperature of 73°F (22.8°C) and an average low-temperature of 56.7°F (13.7°C).

What is the least humid month in Portola Valley?

October is the least humid month in Portola Valley, with an average relative humidity of 68%.

What is the coldest month in Portola Valley?

With an average high-temperature of 55.8°F (13.2°C) and an average low-temperature of 47.1°F (8.4°C), December is the coldest month in Portola Valley, California.

What is the month with the shortest days in Portola Valley?

December has the shortest days of the year, with an average of 9.6h of daylight.

What is the month with the least sunshine in Portola Valley?

The month with the least sunshine is December, with an average of 5.9h of sunshine.

Average temperature
Portola Valley, CA

Average temperature - Portola Valley, CA

The warmest month (with the highest average high temperature) is August (73°F).
The month with the lowest average high temperature is December (55.8°F).

Months with the highest average low temperature are August and September (56.7°F).
The coldest months (with the lowest average low temperature) are January and February (46.4°F).

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Average pressure
Portola Valley, CA

Average pressure - Portola Valley, CA

The month with the highest atmospheric pressure is January (30.13").
The month with the lowest atmospheric pressure is September (29.92").

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Average wind speed
Portola Valley, CA

Average wind speed - Portola Valley, CA

The windiest month (with the highest average wind speed) is April (7.6mph).
The calmest month (with the lowest average wind speed) is August (5.5mph).

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Average humidity
Portola Valley, CA

Average humidity - Portola Valley, CA

The month with the highest relative humidity is March (76%).
The month with the lowest relative humidity is October (68%).

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Average rainfall
Portola Valley, CA

Average rainfall - Portola Valley, CA

The wettest month (with the highest rainfall) is February (0.98").
The driest month (with the least rainfall) is June (0.04").

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Average rainfall days
Portola Valley, CA

Average rainfall days - Portola Valley, CA

The month with the highest number of rainy days is March (10.6 days).
The month with the least rainy days is June (0.9 days).

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Average daylight / Average sunshine
Portola Valley, CA

Average daylight / Average sunshine - Portola Valley, CA

The month with the longest days is June (Average daylight: 14.7h).
The month with the shortest days is December (Average daylight: 9.6h).

The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is December (Average sunshine: 5.9h).

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Average sunshine days
Portola Valley, CA

Average sunshine days - Portola Valley, CA

Months with the most sunshine days are June and July (26.3 days).
The month with the least sunshine days is March (18.3 days).

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Average UV index
Portola Valley, CA

Average UV index - Portola Valley, CA

Months with the highest UV index are June, July, August and September (UV index 5).
Months with the lowest UV index are February, November and December (UV index 3).

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Average visibility
Portola Valley, CA

Average visibility - Portola Valley, CA

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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