September weather forecast and climate
Irvine, CA

The neon-lit city of Irvine in California, with highway lights and the distant hill ranges and skyscape
The neon-lit city of Irvine in California, with highway lights and the distant hill ranges and skyscape
The first month of the autumn, September, is still a warm month in Irvine, California, with average temperature varying between 64.4°F (18°C) and 79°F (26.1°C).

Temperature

In September, the average high-temperature is essentially the same as in August - a still moderately hot 79°F (26.1°C). In September, the average low-temperature is 64.4°F (18°C).

Humidity

The average relative humidity in Irvine is 64%.

Rainfall

In Irvine, in September, it is raining for 4.1 days, with typically 0.31" (8mm) of accumulated precipitation. In Irvine, during the entire year, the rain falls for 63.7 days and collects up to 7.91" (201mm) of precipitation.

Daylight

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

Sunshine

In Irvine, the average sunshine in September is 10.6h.

UV index

Months with the highest UV index in Irvine are June through September, with an average maximum UV index of 6. A UV Index reading of 6 to 7 represents a high health risk from unprotected exposure to the Sun's UV rays for average individuals.
Note: In September, the average maximum UV index of 6 translate into the following recommendations:
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.

What is the temperature in September in Irvine?

In September, in Irvine, California, the average high-temperature is 79°F (26.1°C), and the average low-temperature is 64.4°F (18°C).

What is the average humidity in September in Irvine?

In September, the average relative humidity in Irvine, California, is 64%.

How many days does it rain in September in Irvine?

In Irvine, California, in September, during 4.1 rainfall days, 0.31" (8mm) of precipitation is typically accumulated.

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

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

How long on average sun shines in September in Irvine?

In Irvine, the average sunshine in September is 10.6h.

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

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

What is the UV index reading in September in Irvine?

In Irvine, California, the average daily maximum UV index in September is 6. A UV Index estimate of 6 to 7 represents a high health risk from unsafe exposure to the Sun's UV rays.
Average temperature in September - Irvine, CA
  • Average high temperature in September: 79°F

The warmest month (with the highest average high temperature) is August (79.9°F).
The month with the lowest average high temperature is December (63°F).

  • Average low temperature in September: 64.4°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 (50.5°F).

Average pressure in September - Irvine, 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").

Average wind speed in September - Irvine, CA
  • Average wind speed in September: 4.8mph

The windiest month (with the highest average wind speed) is April (6.2mph).
The calmest months (with the lowest average wind speed) are September and October (4.8mph).

Average humidity in September - Irvine, CA
  • Average humidity in September: 64%

The month with the highest relative humidity is June (71%).
The month with the lowest relative humidity is November (56%).

Average rainfall in September - Irvine, CA
  • Average rainfall in September: 0.31"

The wettest month (with the highest rainfall) is December (1.54").
The driest month (with the least rainfall) is June (0.08").

Average rainfall days in September - Irvine, CA
  • Average rainfall days in September: 4.1 days

The month with the highest number of rainy days is March (7.9 days).
The month with the least rainy days is June (2.2 days).

Average daylight in September / Average sunshine in September - Irvine, 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: 6.6h).

Average sunshine days in September - Irvine, CA
  • Average sunshine days in September: 22.1 days

The month with the most sunshine days is January (24.5 days).
The month with the least sunshine days is May (19.7 days).

Average UV index in September - Irvine, 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, March, November and December (UV index 4).

Average cloud cover in September - Irvine, CA
  • Average cloud cover in September: 10

The month with the most cloud cover is December (Cloud cover 24).
The month with the least cloud cover is August (Cloud cover 7).

Average visibility in September - Irvine, 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).