September weather forecast and climate
Vallejo, CA

A colorful orange sunset skyline seen over the Napa River and Bridge in Vallejo, California
A colorful orange sunset skyline seen over the Napa River and Bridge in Vallejo, California

Weather in September

The first month of the autumn, September, is also a moderately hot month in Vallejo, California, with temperature in the range of an average low of 56.3°F (13.5°C) and an average high of 80.1°F (26.7°C).

Temperature

The warmest months are July and September, with an average high-temperature of 80.1°F (26.7°C).

Humidity

September and October, with an average relative humidity of 60%, are the least humid months in Vallejo.

Rainfall

In Vallejo, California, during September, the rain falls for 2.1 days and regularly aggregates up to 0.08" (2mm) of precipitation. In Vallejo, during the entire year, the rain falls for 56.9 days and collects up to 4.88" (124mm) of precipitation.

Daylight

In Vallejo, the average length of the day in September is 12.4h.

Sunshine

In September, the average sunshine in Vallejo is 11.1h.

UV index

In Vallejo, California, the average daily maximum UV index is 5. A UV Index reading of 3 to 5 represents a medium health hazard from the exposure to the Sun's UV rays for the ordinary person.
Note: The daily maximum UV index of 5 interpret into the following advice:
Take precautions - Protection against sun damage is advised. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. 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 are the warmest months in Vallejo?

July and September, with an average high-temperature of 80.1°F (26.7°C), are warmest months.

What is the temperature in September in Vallejo?

The average high-temperature, in September, in Vallejo, California, is 80.1°F (26.7°C), while the average low-temperature is 56.3°F (13.5°C).

What are the least humid months in Vallejo?

Months with the lowest humidity in Vallejo, California, are September and October, with an average relative humidity of 60%.

What is the average humidity in September in Vallejo?

The average relative humidity in September in Vallejo, California, is 60%.

How many days does it rain in September in Vallejo?

In Vallejo, in September, during 2.1 rainfall days, 0.08" (2mm) of precipitation is typically accumulated.

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

In September, the average length of the day in Vallejo, California, is 12.4h.

How long on average sun shines in September in Vallejo?

In September, the average sunshine in Vallejo, California, is 11.1h.

What is the UV index reading in September in Vallejo?

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

Average temperature in September
Vallejo, CA

Average temperature in September - Vallejo, CA
  • Average high temperature in September: 80.1°F

The warmest months (with the highest average high temperature) are July and September (80.1°F).
The month with the lowest average high temperature is December (55.4°F).

  • Average low temperature in September: 56.3°F

The month with the highest average low temperature is August (56.5°F).
The coldest month (with the lowest average low temperature) is January (43°F).

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Average pressure in September
Vallejo, CA

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

The month with the highest atmospheric pressure is January (30.14").
The month with the lowest atmospheric pressure is June (29.91").

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Average wind speed in September
Vallejo, CA

Average wind speed in September - Vallejo, CA
  • Average wind speed in September: 5.5mph

The windiest month (with the highest average wind speed) is May (7.1mph).
The calmest month (with the lowest average wind speed) is November (4.6mph).

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Average humidity in September
Vallejo, CA

Average humidity in September - Vallejo, CA
  • Average humidity in September: 60%

The month with the highest relative humidity is March (75%).
Months with the lowest relative humidity are September and October (60%).

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Average rainfall in September
Vallejo, CA

Average rainfall in September - Vallejo, CA
  • Average rainfall in September: 0.08"

The wettest month (with the highest rainfall) is February (1.14").
The driest months (with the least rainfall) are July and August (0.04").

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Average rainfall days in September
Vallejo, CA

Average rainfall days in September - Vallejo, CA
  • Average rainfall days in September: 2.1 days

The month with the highest number of rainy days is March (10.2 days).
The month with the least rainy days is August (0.9 days).

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

Average daylight in September / Average sunshine in September - Vallejo, 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: 9.6h).

  • Average sunshine in September: 11.1h

The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is December (Average sunshine: 5.7h).

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Average sunshine days in September
Vallejo, CA

Average sunshine days in September - Vallejo, CA
  • Average sunshine days in September: 26 days

The month with the most sunshine days is July (27.2 days).
The month with the least sunshine days is March (18.8 days).

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Average UV index in September
Vallejo, CA

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

The month with the highest UV index is June (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
Vallejo, CA

Average cloud cover in September - Vallejo, CA
  • Average cloud cover in September: 11

The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is July (Cloud cover 9).

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Average visibility in September
Vallejo, CA

Average visibility in September - Vallejo, 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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