September weather forecast
Sonoma, CA

Neat rows of vines in a vineyard farm in Sonoma, California
Neat rows of vines in a vineyard farm in Sonoma, California

Weather in September

September, the first month of the autumn, in Sonoma, is also a moderately hot month, with temperature in the range of an average low of 54.7°F (12.6°C) and an average high of 81.1°F (27.3°C).

Temperature

In September, the average high-temperature is almost the same as in August - a still moderately hot 81.1°F (27.3°C). In September, in Sonoma, the average low-temperature is 54.7°F (12.6°C).

Heat index

The average heat index is calculated to be 83.1°F (28.4°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 'feels like', 'felt air temperature', 'real feel', or 'apparent temperature', is what the temperature feels like to the human body when the air temperature is combined with the relative humidity. Additional factors like activity, clothing, differences in body mass, height, and shape, and metabolic differences affect individual temperature impact. Be aware that direct exposure to sunlight increases heat impact and may raise the heat index 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

With an average relative humidity of 59%, September is the least humid month.

Rainfall

In Sonoma, during September, the rain falls for 2.4 days and regularly aggregates up to 0.08" (2mm) of precipitation. Throughout the year, in Sonoma, there are 73.3 rainfall days, and 15.47" (393mm) of precipitation is accumulated.

Daylight

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

Sunshine

In Sonoma, the average sunshine in September is 11h.

UV index

In September, the average daily maximum UV index in Sonoma is 5. A UV Index value of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV radiation for ordinary individuals.
Note: The average daily UV index of 5 transform into the following instructions:
Take precautions - Protection against sun damage is advised. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the temperature in September in Sonoma?

In Sonoma, in September, the average high-temperature is 81.1°F (27.3°C), and the average low-temperature is 54.7°F (12.6°C). In September, the average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which calculates the temperature value influenced by the moisture in the air, is calculated to be 83.1°F (28.4°C).

What is the least humid month in Sonoma?

The least humid month in Sonoma is September, with an average relative humidity of 59%.

What is the average humidity in September in Sonoma?

In Sonoma, the average relative humidity in September is 59%.

How many days does it rain in September in Sonoma?

In Sonoma, during September, the rain falls for 2.4 days and regularly aggregates up to 0.08" (2mm) of precipitation.

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

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

How many hours of sunshine does Sonoma have in September?

The average sunshine in September is 11h.

What is the UV index intensity in September in Sonoma?

The average daily maximum UV index in September in Sonoma, California, is 5. A UV Index value of 3 to 5 symbolizes a medium hazard to health from the exposure to the Sun's UV radiation.

Average temperature in September
Sonoma, CA

Average temperature in September - Sonoma, CA
  • Average high temperature in September: 27.3°C

The warmest month (with the highest average high temperature) is August (28.3°C).
The month with the lowest average high temperature is December (12.8°C).

  • Average low temperature in September: 12.6°C

The month with the highest average low temperature is August (12.7°C).
The coldest month (with the lowest average low temperature) is December (5.2°C).

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Average pressure in September
Sonoma, CA

Average pressure in September - Sonoma, CA
  • Average pressure in September: 1013.1mbar

The month with the highest atmospheric pressure is January (1020.4mbar).
The month with the lowest atmospheric pressure is June (1013mbar).

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Average wind speed in September
Sonoma, CA

Average wind speed in September - Sonoma, CA
  • Average wind speed in September: 7.7km/h

The windiest month (with the highest average wind speed) is May (10km/h).
The calmest month (with the lowest average wind speed) is November (7.1km/h).

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Average humidity in September
Sonoma, CA

Average humidity in September - Sonoma, CA
  • Average humidity in September: 59%

The month with the highest relative humidity is March (76%).
The month with the lowest relative humidity is September (59%).

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Average rainfall in September
Sonoma, CA

Average rainfall in September - Sonoma, CA
  • Average rainfall in September: 2mm

The wettest month (with the highest rainfall) is February (87mm).
The driest months (with the least rainfall) are July and August (1mm).

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Average rainfall days in September
Sonoma, CA

Average rainfall days in September - Sonoma, CA
  • Average rainfall days in September: 2.4 days

The month with the highest number of rainy days is March (13.4 days).
The month with the least rainy days is August (0.8 days).

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

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

The month with the longest days is June (Average daylight: 14.8h).
The month with the shortest days is December (Average daylight: 9.5h).

  • Average sunshine in September: 11h

The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is December (Average sunshine: 5.6h).

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Average sunshine days in September
Sonoma, CA

Average sunshine days in September - Sonoma, CA
  • Average sunshine days in September: 26.7 days

The month with the most sunshine days is July (28.7 days).
The month with the least sunshine days is March (16.1 days).

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Average UV index in September
Sonoma, CA

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

Months with the highest UV index are June and July (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
Sonoma, CA

Average cloud cover in September - Sonoma, CA
  • Average cloud cover in September: 10

The month with the most cloud cover is March (Cloud cover 40).
The month with the least cloud cover is July (Cloud cover 8).

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Average visibility in September
Sonoma, CA

Average visibility in September - Sonoma, CA
  • Average visibility in September: 10km

Months with the highest visibility are June, July and September (10km).
Months with the lowest visibility are January, February, March, April, May, August, October, November and December (9km).

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