San Diego
California, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
San Diego, CA

The view of Coronado Island in San Diego, California, from across a water body on a sidewalk, with a row of palm trees
The view of Coronado Island in San Diego, California, from across a water body on a sidewalk, with a row of palm trees
The first month of the autumn, September, is also a moderately hot month in San Diego, California, with average temperature ranging between max 76.6°F (24.8°C) and min 65.1°F (18.4°C).

Temperature

In September, the average high-temperature is almost the same as in August - a still moderately hot 76.6°F (24.8°C). The average low-temperature, in September, is 65.1°F (18.4°C).

Humidity

In San Diego, the average relative humidity is 68%.

Rainfall

In September, in San Diego, the rain falls for 4.5 days. Throughout September, 0.39" (10mm) of precipitation is accumulated. In San Diego, during the entire year, the rain falls for 61.8 days and collects up to 8.7" (221mm) of precipitation.

Ocean temperature

In San Diego, in September, the average water temperature is 66.7°F (19.3°C).
Note: For swimming, a surface water temperature of 66.7°F (19.3°C) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 69.8°F (21°C).

Daylight

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

Sunshine

In September, the average sunshine in San Diego, California, is 10.3h.

UV index

Months with the highest UV index are July through September, with an average maximum UV index of 6. A UV Index value of 6 to 7 symbolizes a high health risk from unprotected exposure to the Sun's UV rays for average individuals.
Note: The daily maximum UV index of 6 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.

What is the temperature in September in San Diego?

The average high-temperature, in September, in San Diego, California, is 76.6°F (24.8°C), while the average low-temperature is 65.1°F (18.4°C).

What is the average humidity in September in San Diego?

The average relative humidity in September in San Diego, California, is 68%.

How much does it rain in San Diego in September?

In San Diego, California, in September, it is raining for 4.5 days, with typically 0.39" (10mm) of accumulated precipitation.

How cold is the water in September in San Diego?

In San Diego, the average seawater temperature in September is 66.7°F (19.3°C). For swimming, a surface water temperature of 66.7°F (19.3°C) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 69.8°F (21°C).

How many hours of daylight does San Diego have in September?

In San Diego, California, the average length of the day in September is 12.4h.

How many hours of sunshine does San Diego have in September?

In September, the average sunshine is 10.3h.

What are the months with the highest UV index in San Diego?

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

What is the UV index intensity in September in San Diego?

The average daily maximum UV index in September in San Diego is 6. A UV Index reading of 6 to 7 represents a high health vulnerability from unprotected exposure to the UV radiation.
Average temperature in September - San Diego, CA
  • Average high temperature in September: 76.6°F

The warmest month (with the highest average high temperature) is August (77.4°F).
The month with the lowest average high temperature is February (63.1°F).

  • Average low temperature in September: 65.1°F

The month with the highest average low temperature is August (65.7°F).
The coldest month (with the lowest average low temperature) is February (51.8°F).

Average humidity in September - San Diego, CA
  • Average humidity in September: 68%

The month with the highest relative humidity is June (73%).
The month with the lowest relative humidity is November (59%).

Average rainfall in September - San Diego, CA
  • Average rainfall in September: 0.39"

The wettest month (with the highest rainfall) is December (1.65").
The driest month (with the lowest rainfall) is June (0.12").

Average rainfall days in September - San Diego, CA
  • Average rainfall days in September: 4.5 days

The month with the highest number of rainy days is March (7.6 days).
The month with the lowest number of rainy days is June (2.7 days).

Average sea temperature in September - San Diego, CA
  • Average sea temperature in September: 66.7°F

The best month for swimming (with the highest average sea temperature) is August (67.9°F).
The coldest month (with the lowest average sea temperature) is February (58.7°F).

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

The month with the longest days is June (Average daylight: 14.3h).
The month with shortest days is December (Average daylight: 10h).

  • Average sunshine in September: 10.3h

Months with most sunshine are July and August (Average sunshine: 11.9h).
The month with least sunshine is December (Average sunshine: 6.7h).

Average UV index in September - San Diego, CA
  • Average UV index in September: 6

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