September weather forecastCosta Mesa, CA
September
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.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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).
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).
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).
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%).
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").
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).
Average daylight in September /
Average sunshine in September
Costa Mesa, CA
- Average daylight in September: 12h and 24min
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 30min
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).
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).
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).
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).
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).
