September weather forecast and climate
Fullerton, CA

Trees and neat lawns of the famous Muckenthaler Community Center in Fullerton, California
Trees and neat lawns of the famous Muckenthaler Community Center in Fullerton, California

Weather in September

September, the first month of the autumn, in Fullerton, is also a moderately hot month, with average temperature varying between 64.8°F (18.2°C) and 82.2°F (27.9°C).

Temperature

In September, the average high-temperature is almost the same as in August - a still moderately hot 82.2°F (27.9°C). In September, the average low-temperature is 64.8°F (18.2°C).

Heat index

In September, the average heat index is calculated to 84.4°F (29.1°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', combines air temperature and relative humidity to represent a human perceived temperature equivalent. This effect is individual, with diverse people perceiving weather differently for numerous reasons (wind, clothing, metabolic differences), and activity. 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 especially crucial for babies and toddlers. 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 Fullerton, the average relative humidity is 58%.

Rainfall

In Fullerton, California, during September, the rain falls for 3.5 days and regularly aggregates up to 0.2" (5mm) of precipitation. Throughout the year, in Fullerton, there are 52.5 rainfall days, and 7.09" (180mm) of precipitation is accumulated.

Daylight

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

Sunshine

The average sunshine in September is 10.6h.

UV index

Months with the highest UV index are June through September, with an average maximum UV index of 6. A UV Index of 6 to 7 symbolizes a high health hazard from unprotected exposure to the Sun's UV rays for ordinary individuals.
Note: The daily maximum UV index of 6 in September interpret into the following advice:
Take precautions against overexposure. Protection against sun damage is needed. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. 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 Fullerton?

In Fullerton, California, in September, the average high-temperature is 82.2°F (27.9°C), and the average low-temperature is 64.8°F (18.2°C). In September, the average heat index (a.k.a. 'feels like', 'apparent temperature'), that factores the actual air temperature with the relative humidity, is evaluated at 84.4°F (29.1°C).

What is the average humidity in September in Fullerton?

In Fullerton, California, the average relative humidity in September is 58%.

How much does it rain in Fullerton in September?

In September, in Fullerton, California, the rain falls for 3.5 days. Throughout September, 0.2" (5mm) of precipitation is accumulated.

How many hours of daylight does Fullerton have in September?

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

How long on average sun shines in September in Fullerton?

The average sunshine in September in Fullerton, California, is 10.6h.

What is the month with the highest UV index in Fullerton?

Months with the highest UV index in Fullerton, California, are June through September, with an average maximum UV index of 6.

What is the UV index intensity in September in Fullerton?

In Fullerton, California, the average daily maximum UV index in September is 6. A UV Index of 6 to 7 symbolizes a high health vulnerability from unprotected exposure to the UV radiation.

Average temperature in September
Fullerton, CA

Average temperature in September - Fullerton, CA
  • Average high temperature in September: 82.2°F

The warmest month (with the highest average high temperature) is August (83.5°F).
The month with the lowest average high temperature is December (64°F).

  • Average low temperature in September: 64.8°F

The month with the highest average low temperature is August (65.5°F).
The coldest month (with the lowest average low temperature) is February (50.2°F).

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Average pressure in September
Fullerton, CA

Average pressure in September - Fullerton, CA
  • Average pressure in September: 29.89"

The month with the highest atmospheric pressure is January (30.1").
The month with the lowest atmospheric pressure is June (29.88").

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Average wind speed in September
Fullerton, CA

Average wind speed in September - Fullerton, CA
  • Average wind speed in September: 4.7mph

The windiest month (with the highest average wind speed) is April (6mph).
The calmest months (with the lowest average wind speed) are September and October (4.7mph).

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Average humidity in September
Fullerton, CA

Average humidity in September - Fullerton, CA
  • Average humidity in September: 58%

The month with the highest relative humidity is June (65%).
The month with the lowest relative humidity is November (51%).

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Average rainfall in September
Fullerton, CA

Average rainfall in September - Fullerton, CA
  • Average rainfall in September: 0.2"

The wettest month (with the highest rainfall) is December (1.54").
The driest month (with the least rainfall) is June (0.04").

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Average rainfall days in September
Fullerton, CA

Average rainfall days in September - Fullerton, CA
  • Average rainfall days in September: 3.5 days

The month with the highest number of rainy days is March (7.3 days).
The month with the least rainy days is June (1.5 days).

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

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

The month with the longest days is June (Average daylight: 14.4h).
The month with the shortest days is December (Average daylight: 9.9h).

  • Average sunshine in September: 10.6h

Months with the most sunshine are July and August (Average sunshine: 12h).
The month with the least sunshine is December (Average sunshine: 6.7h).

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Average sunshine days in September
Fullerton, CA

Average sunshine days in September - Fullerton, CA
  • Average sunshine days in September: 23.4 days

The month with the most sunshine days is August (25.8 days).
The month with the least sunshine days is February (20.6 days).

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Average UV index in September
Fullerton, CA

Average UV index in September - Fullerton, CA
  • Average UV index in September: 6

Months with the highest UV index are June, July, August and September (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 4).

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Average cloud cover in September
Fullerton, CA

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

Months with the most cloud cover are March and December (Cloud cover 22).
The month with the least cloud cover is August (Cloud cover 5).

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Average visibility in September
Fullerton, CA

Average visibility in September - Fullerton, 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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