September weather forecast
Costa Mesa, CA

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Weather in September

The first month of the autumn, September, is also a moderately hot month in Costa Mesa, California, with an average temperature ranging between max 76.1°F (24.5°C) and min 64.2°F (17.9°C).

Temperature

Costa Mesa ushers in September with an average high-temperature of a still moderately hot 76.1°F (24.5°C), showing a close resemblance to the previous month. During the month of September, Costa Mesa anticipates a mean low-temperature of 64.2°F (17.9°C).

Humidity

In September, the average relative humidity in Costa Mesa is 68%.

Rainfall

In Costa Mesa, in September, during 3.3 rainfall days, 0.16" (4mm) of precipitation is typically accumulated. In Costa Mesa, during the entire year, the rain falls for 50.7 days and collects up to 3.74" (95mm) of precipitation.

Daylight

In September, the average length of the day in Costa Mesa is 12h and 22min.
On the first day of September in Costa Mesa, sunrise is at 6:26 am and sunset at 7:16 pm. On the last day of the month, sunrise is at 6:45 am and sunset at 6:36 pm PDT.

Sunshine

In September, the average sunshine is 10.5h.

UV index

The months with the highest UV index in Costa Mesa are July through September, with an average maximum UV index of 6. A UV Index estimate of 6 to 7 represents a high health hazard from unprotected exposure to Sun's UV rays for average individuals.
Note: A maximum high UV index of 6 in September translates into the following recommendations:
Implement preventive steps and embrace sun safety standards. Protection from skin and eye distress is compulsory. During the period from 10 a.m. to 4 p.m., UV radiation is highest. Try to avoid direct sunlight during these hours. To cut down UV radiation exposure by about half, sport a wide-brim hat.
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Frequently asked questions

What is the average September temperature in Costa Mesa?

In September, the average high-temperature and low-temperature in Costa Mesa are 76.1°F (24.5°C) and 64.2°F (17.9°C) respectively.

What is the average humidity in September in Costa Mesa?

The average relative humidity in September in Costa Mesa is 68%.

How much does it rain in Costa Mesa in September?

In Costa Mesa, in September, during 3.3 rainfall days, 0.16" (4mm) of precipitation is typically accumulated.

How many hours of daylight does Costa Mesa have in September?

The average day length in September is 12h and 22min.

When is the sunrise / sunset in September in Costa Mesa?

In September, on the first day of the month, sunrise is at 6:26 am and sunset at 7:16 pm. On the last day of the month, in Costa Mesa, sunrise is at 6:45 am and sunset at 6:36 pm PDT.

How many hours of sunshine does Costa Mesa have in September?

In Costa Mesa, the average sunshine duration in September is 10.5h.

When is the highest UV index in Costa Mesa?

July through September, with an average maximum UV index of 6, are months with the highest UV index in Costa Mesa, California.

What is the UV index intensity in September in Costa Mesa?

In September, the average daily maximum UV index in Costa Mesa, California, is 6. A UV Index estimate of 6 to 7 represents a high hazard to health from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Costa Mesa, CA

Average temperature in September - Costa Mesa, CA
  • Average high temperature in September: 76.1°F

The warmest month (with the highest average high temperature) is August (76.6°F).
The month with the lowest average high temperature is December (62.4°F).

  • Average low temperature in September: 64.2°F

The month with the highest average low temperature is August (64.9°F).
The coldest month (with the lowest average low temperature) is February (52.3°F).

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Average pressure in September
Costa Mesa, CA

Average pressure in September - Costa Mesa, CA
  • Average pressure in September: 29.89"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are June and September (29.89"Hg).

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Average wind speed in September
Costa Mesa, CA

Average wind speed in September - Costa Mesa, CA
  • Average wind speed in September: 5.3mph

The windiest month (with the highest average wind speed) is April (6.6mph).
The calmest month (with the lowest average wind speed) is October (5.2mph).

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Average humidity in September
Costa Mesa, CA

Average humidity in September - Costa Mesa, CA
  • Average humidity in September: 68%

The month with the highest relative humidity is June (74%).
The month with the lowest relative humidity is November (59%).

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Average rainfall in September
Costa Mesa, CA

Average rainfall in September - Costa Mesa, CA
  • Average rainfall in September: 0.16"

The wettest month (with the highest rainfall) is December (0.79").
The driest month (with the least rainfall) is June (0.04").

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Average rainfall days in September
Costa Mesa, CA

Average rainfall days in September - Costa Mesa, CA
  • Average rainfall days in September: 3.3 days

The month with the highest number of rainy days is March (6.6 days).
The month with the least rainy days is June (1.6 days).

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Average daylight in September /
Average sunshine in September
Costa Mesa, CA

Average daylight in September / Average sunshine in September - Costa Mesa, CA
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 10h and 0min).

  • Average sunshine in September: 10h and 3min

The month with the most sunshine is August (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 36min).

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Average sunshine days in September
Costa Mesa, CA

Average sunshine days in September - Costa Mesa, CA
  • Average sunshine days in September: 24.5 days

The month with the most sunshine days is June (26.5 days).
The month with the least sunshine days is February (20.5 days).

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Average UV index in September
Costa Mesa, CA

Average UV index in September - Costa Mesa, CA
  • Average UV index in September: 6

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

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Average cloud cover in September
Costa Mesa, CA

Average cloud cover in September - Costa Mesa, CA
  • Average cloud cover in September: 11

The months with the most cloud cover are March and December (Cloud cover 24).
The month with the least cloud cover is August (Cloud cover 8).

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Average visibility in September
Costa Mesa, CA

Average visibility in September - Costa Mesa, CA
  • Average visibility in September: 6mi

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

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Costa Mesa, California, USA

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