September weather forecast and climate
O'Brien, CA

Weather in September

The first month of the autumn, September, is also a moderately hot month in O'Brien, California, with average temperature ranging between max 84°F (28.9°C) and min 54.3°F (12.4°C).

Temperature

In O'Brien, California, the average high-temperature in September marginally drops, from a tropical 90.1°F (32.3°C) in August, to a warm 84°F (28.9°C). In September, in O'Brien, the average low-temperature is 54.3°F (12.4°C).

Heat index

The average heat index in September is estimated at 83.3°F (28.5°C). Exhaustion is likely with prolonged exposure and activity. Sustaining activity may result in heat cramps.
Note that heat index values are valued for light wind and location in the shade. With the exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature', 'real feel', 'apparent temperature', or 'feels like', combines air temperature and relative humidity to represent a human perceived temperature equivalent. Additional factors like activity, differences in body mass, height, and shape, pregnancy, and wind affect individual temperature impact. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

In O'Brien, the average relative humidity is 40%.

Rainfall

In O'Brien, it is raining for 3.4 days, with typically 0.31" (8mm) of accumulated precipitation. Throughout the year, there are 102.3 rainfall days, and 24.21" (615mm) of precipitation is accumulated.

Snowfall

In O'Brien snow does not fall in April through October.

Daylight

In O'Brien, the average length of the day is 12.4h.

Sunshine

In September, the average sunshine in O'Brien, California, is 11h.

UV index

In O'Brien, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a medium health hazard from the exposure to the Sun's UV radiation for the average person.
Note: In September, the average maximum UV index of 5 translate into the following recommendations:
Take precautions - Protection against the skin and eye damage is obliged. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.
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FAQ

What is the temperature in September in O'Brien?

In O'Brien, in September, the average high-temperature is 84°F (28.9°C), and the average low-temperature is 54.3°F (12.4°C). The average heat index (a.k.a. 'real feel', 'apparent temperature'), that takes the relative humidity and factores it into the air temperature reading, in September is calculated to 83.3°F (28.5°C).

What is the average humidity in September in O'Brien?

The average relative humidity in September in O'Brien is 40%.

How much does it rain in O'Brien in September?

In September, in O'Brien, California, the rain falls for 3.4 days. Throughout September, 0.31" (8mm) of precipitation is accumulated.

When it does not snow in O'Brien?

In O'Brien snow does not fall in April through October.

What is the average length of the day in September in O'Brien?

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

How long on average sun shines in September in O'Brien?

The average sunshine in September in O'Brien, California, is 11h.

How high is the UV index in September in O'Brien?

The average daily maximum UV index in September in O'Brien is 5. A UV Index value of 3 to 5 symbolizes a medium health risk from unsafe exposure to the Sun's UV rays.

Average temperature in September
O'Brien, CA

Average temperature in September - O
  • Average high temperature in September: 84°F

The warmest month (with the highest average high temperature) is July (91.6°F).
The month with the lowest average high temperature is December (47.8°F).

  • Average low temperature in September: 54.3°F

The month with the highest average low temperature is July (59.4°F).
The coldest month (with the lowest average low temperature) is December (33.6°F).

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Average pressure in September
O'Brien, CA

Average pressure in September - O
  • Average pressure in September: 29.95"

The month with the highest atmospheric pressure is January (30.16").
The month with the lowest atmospheric pressure is August (29.92").

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Average wind speed in September
O'Brien, CA

Average wind speed in September - O
  • Average wind speed in September: 5mph

The windiest months (with the highest average wind speed) are March and October (5.3mph).
The calmest months (with the lowest average wind speed) are August and November (4.5mph).

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Average humidity in September
O'Brien, CA

Average humidity in September - O
  • Average humidity in September: 40%

The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is August (37%).

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Average rainfall in September
O'Brien, CA

Average rainfall in September - O
  • Average rainfall in September: 0.31"

The wettest month (with the highest rainfall) is March (4.8").
The driest month (with the least rainfall) is July (0.12").

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Average rainfall days in September
O'Brien, CA

Average rainfall days in September - O
  • Average rainfall days in September: 3.4 days

The month with the highest number of rainy days is March (16.8 days).
The month with the least rainy days is August (1.7 days).

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Average snowfall in September
O'Brien, CA

Average snowfall in September - O
  • Average snowfall in September: 0"

The month with the highest snowfall is November (1.3").
Months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days in September
O'Brien, CA

Average snowfall days in September - O
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (1.9 days).
Months with the least snowfall days are April, May, June, July, August, September and October (0 days).

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Average daylight in September /
Average sunshine in September
O'Brien, CA

Average daylight in September / Average sunshine in September - O
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 15.1h).
The month with the shortest days is December (Average daylight: 9.3h).

  • Average sunshine in September: 11h

The month with the most sunshine is July (Average sunshine: 12.2h).
The month with the least sunshine is December (Average sunshine: 5.3h).

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Average sunshine days in September
O'Brien, CA

Average sunshine days in September - O
  • Average sunshine days in September: 25.2 days

The month with the most sunshine days is August (27.1 days).
The month with the least sunshine days is March (11.8 days).

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Average UV index in September
O'Brien, CA

Average UV index in September - O
  • Average UV index in September: 5

The month with the highest UV index is July (UV index 7).
Months with the lowest UV index are February, November and December (UV index 2).

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Average cloud cover in September
O'Brien, CA

Average cloud cover in September - O
  • Average cloud cover in September: 9

The month with the most cloud cover is March (Cloud cover 44).
The month with the least cloud cover is August (Cloud cover 5).

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Average visibility in September
O'Brien, CA

Average visibility in September - O
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October and November (6mi).
The month with the lowest visibility is December (5mi).

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