September weather forecast
Palo Alto, CA

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Palm trees and the iconic Hoover Tower within Stanford University in Palo Alto, California
Palm trees and the iconic Hoover Tower within Stanford University in Palo Alto, California

Weather in September

September, the first month of the autumn in Palo Alto, is also a moderately hot month, with an average temperature ranging between max 76.5°F (24.7°C) and min 56.7°F (13.7°C).

Temperature

The average high-temperature for September is a still moderately hot 76.5°F (24.7°C), closely aligning with the temperature of the preceding month. Palo Alto experiences a steady low-temperature of 56.7°F (13.7°C) throughout September.

Humidity

The months with the lowest humidity are September and October, with an average relative humidity of 65%.

Rainfall

In Palo Alto, during September, the rain falls for 2.1 days and regularly aggregates up to 0.08" (2mm) of precipitation. In Palo Alto, during the entire year, the rain falls for 63.3 days and collects up to 9.53" (242mm) of precipitation.

Daylight

The average length of the day in September in Palo Alto is 12h and 25min.
On the first day of the month, sunrise is at 6:39 am and sunset at 7:36 pm. On the last day of September, in Palo Alto, sunrise is at 7:03 am and sunset at 6:52 pm PDT.

Sunshine

In Palo Alto, California, the average sunshine in September is 11h.

UV index

The months with the highest UV index in Palo Alto are April through October, with an average maximum UV index of 5. A UV Index value of 3 to 5 symbolizes a medium health hazard from unsafe exposure to UV radiation for the ordinary person.
Note: During September, 5 as the daily maximum UV index converts into the following advice:
Preventative actions are necessary - Suggestions to safeguard against sun damage are in order. The solar radiation around mid-day is intense; avoid the Sun and stay safe. Clothes that are both tight-knit and comfortably loose are prime choices for sun protection.
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Frequently asked questions

What is the temperature in September in Palo Alto?

In Palo Alto, in September, the average high-temperature is 76.5°F (24.7°C), and the average low-temperature is 56.7°F (13.7°C).

What are the least humid months in Palo Alto?

September and October, with an average relative humidity of 65%, are the least humid months in Palo Alto, California.

What is the average humidity in September in Palo Alto?

The average relative humidity in September is 65%.

How many days does it rain in September in Palo Alto?

In Palo Alto, California, in September, it is raining for 2.1 days, with typically 0.08" (2mm) of accumulated precipitation.

What is the average length of the day in September in Palo Alto?

The average day length in September is 12h and 25min.

When are sunrise and sunset in September in Palo Alto?

On the first day of September in Palo Alto, California, sunrise is at 6:39 am and sunset at 7:36 pm. On the last day of the month, sunrise is at 7:03 am and sunset at 6:52 pm PDT.

How long on average sun shines in September in Palo Alto?

In Palo Alto, California, the average sunshine duration in September is 11h.

When is the highest UV index in Palo Alto?

The months with the highest UV index in Palo Alto are April through October, with an average maximum UV index of 5.

What is the UV index intensity in September in Palo Alto?

The average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate health threat from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Palo Alto, CA

Average temperature in September - Palo Alto, CA
  • Average high temperature in September: 76.5°F

The warmest months (with the highest average high temperature) are July and August (77.5°F).
The month with the lowest average high temperature is December (56.3°F).

  • Average low temperature in September: 56.7°F

The month with the highest average low temperature is August (57°F).
The coldest months (with the lowest average low temperature) are January and February (45.1°F).

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Average pressure in September
Palo Alto, CA

Average pressure in September - Palo Alto, CA
  • Average pressure in September: 29.92"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June and September (29.92"Hg).

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Average wind speed in September
Palo Alto, CA

Average wind speed in September - Palo Alto, CA
  • Average wind speed in September: 4.9mph

The windiest months (with the highest average wind speed) are April and May (6.5mph).
The calmest months (with the lowest average wind speed) are September and October (4.9mph).

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Average humidity in September
Palo Alto, CA

Average humidity in September - Palo Alto, CA
  • Average humidity in September: 65%

The month with the highest relative humidity is March (74%).
The months with the lowest relative humidity are September and October (65%).

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Average rainfall in September
Palo Alto, CA

Average rainfall in September - Palo Alto, CA
  • Average rainfall in September: 0.08"

The wettest month (with the highest rainfall) is February (2.01").
The driest month (with the least rainfall) is July (0").

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Average rainfall days in September
Palo Alto, CA

Average rainfall days in September - Palo Alto, CA
  • Average rainfall days in September: 2.1 days

The month with the highest number of rainy days is March (12.3 days).
The month with the least rainy days is August (0.6 days).

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Average daylight in September /
Average sunshine in September
Palo Alto, CA

Average daylight in September / Average sunshine in September - Palo Alto, CA
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).

  • Average sunshine in September: 11h and 0min

The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).

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Average sunshine days in September
Palo Alto, CA

Average sunshine days in September - Palo Alto, CA
  • Average sunshine days in September: 27.6 days

The month with the most sunshine days is July (30.2 days).
The month with the least sunshine days is March (18 days).

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Average UV index in September
Palo Alto, CA

Average UV index in September - Palo Alto, CA
  • Average UV index in September: 5

The months with the highest UV index are April, May, June, July, August, September and October (UV index 5).
The months with the lowest UV index are February, November and December (UV index 3).

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Average cloud cover in September
Palo Alto, CA

Average cloud cover in September - Palo Alto, CA
  • Average cloud cover in September: 11

The months with the most cloud cover are March and December (Cloud cover 34).
The month with the least cloud cover is July (Cloud cover 6).

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Average visibility in September
Palo Alto, CA

Average visibility in September - Palo Alto, CA
  • Average visibility in September: 6mi

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

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Palo Alto, California, USA

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