September weather forecast and climate
Livermore, CA

A path in the scenic hilly and forest landscape of the famous Lake Del Valle Regional Park in Livermore, California
A path in the scenic hilly and forest landscape of the famous Lake Del Valle Regional Park in Livermore, California

Weather in September

September, the first month of the autumn, in Livermore, is still a warm month, with average temperature varying between 56.5°F (13.6°C) and 82.9°F (28.3°C).

Temperature

In September, the average high-temperature is almost the same as in August - a still moderately hot 82.9°F (28.3°C). In Livermore, in September, the average low-temperature is 56.5°F (13.6°C).

Heat index

The average heat index is appraised at 84.7°F (29.3°C). Exhaustion is likely with prolonged exposure and activity. Sustaining activity may result in heat cramps.
Take into consideration that the heat index values are calculated for shade and light wind conditions. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel', 'apparent temperature', 'felt air temperature', or 'feels like', is a measure of how hot it feels when the actual air humidity is factored in. Additional factors like metabolic differences, differences in body mass, height, and shape, pregnancy, and activity influence one's weather impression. Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.

Humidity

July and September, with an average relative humidity of 55%, are the least humid months in Livermore.

Rainfall

In Livermore, during 2.3 rainfall days, 0.16" (4mm) of precipitation is typically accumulated. In Livermore, California, during the entire year, the rain falls for 70.6 days and collects up to 11.3" (287mm) of precipitation.

Daylight

The average length of the day in September is 12.4h.

Sunshine

In Livermore, the average sunshine in September is 11.3h.

UV index

The average daily maximum UV index in Livermore, California, is 5. A UV Index of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to the UV radiation for the average person.
Note: The daily maximum UV index of 5 interpret into the following advice:
Take precautions - Protection against the skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
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FAQ

What is the temperature in September in Livermore?

In September, the average high-temperature is 82.9°F (28.3°C), and the average low-temperature is 56.5°F (13.6°C). In September, the average heat index (a.k.a. 'real feel', 'felt air temperature'), that calculates temperature value influenced by the moisture in the air, is appraised at 84.7°F (29.3°C).

What are the least humid months in Livermore?

Months with the lowest humidity in Livermore are July and September, with an average relative humidity of 55%.

What is the average humidity in September in Livermore?

In September, the average relative humidity in Livermore, California, is 55%.

How many days does it rain in September in Livermore?

In Livermore, in September, it is raining for 2.3 days, with typically 0.16" (4mm) of accumulated precipitation.

What is the average length of the day in September in Livermore?

The average length of the day in September in Livermore, California, is 12.4h.

How many hours of sunshine does Livermore have in September?

In Livermore, California, the average sunshine in September is 11.3h.

How high is the UV index in September in Livermore?

In September, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a medium hazard to health from the exposure to the Sun's UV rays.

Average temperature in September
Livermore, CA

Average temperature in September - Livermore, CA
  • Average high temperature in September: 82.9°F

The warmest month (with the highest average high temperature) is July (86°F).
The month with the lowest average high temperature is December (54.9°F).

  • Average low temperature in September: 56.5°F

The month with the highest average low temperature is August (56.7°F).
The coldest month (with the lowest average low temperature) is January (41.4°F).

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Average pressure in September
Livermore, CA

Average pressure in September - Livermore, CA
  • Average pressure in September: 29.92"

The month with the highest atmospheric pressure is January (30.14").
Months with the lowest atmospheric pressure are June, August and September (29.92").

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Average wind speed in September
Livermore, CA

Average wind speed in September - Livermore, CA
  • Average wind speed in September: 5.2mph

The windiest months (with the highest average wind speed) are May and June (6.5mph).
The calmest month (with the lowest average wind speed) is November (4.2mph).

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Average humidity in September
Livermore, CA

Average humidity in September - Livermore, CA
  • Average humidity in September: 55%

The month with the highest relative humidity is March (74%).
Months with the lowest relative humidity are July and September (55%).

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Average rainfall in September
Livermore, CA

Average rainfall in September - Livermore, CA
  • Average rainfall in September: 0.16"

The wettest month (with the highest rainfall) is February (2.09").
The driest month (with the least rainfall) is August (0.04").

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Average rainfall days in September
Livermore, CA

Average rainfall days in September - Livermore, CA
  • Average rainfall days in September: 2.3 days

The month with the highest number of rainy days is March (12.7 days).
The month with the least rainy days is August (1.3 days).

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Average daylight in September /
Average sunshine in September
Livermore, CA

Average daylight in September / Average sunshine in September - Livermore, CA
  • Average daylight in September: 12.4h

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

  • Average sunshine in September: 11.3h

The month with the most sunshine is July (Average sunshine: 12.1h).
The month with the least sunshine is December (Average sunshine: 6h).

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Average sunshine days in September
Livermore, CA

Average sunshine days in September - Livermore, CA
  • Average sunshine days in September: 26.5 days

The month with the most sunshine days is August (28.8 days).
The month with the least sunshine days is March (17.6 days).

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Average UV index in September
Livermore, CA

Average UV index in September - Livermore, CA
  • Average UV index in September: 5

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 3).

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Average cloud cover in September
Livermore, CA

Average cloud cover in September - Livermore, CA
  • Average cloud cover in September: 9

The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 5).

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Average visibility in September
Livermore, CA

Average visibility in September - Livermore, CA
  • Average visibility in September: 6mi

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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