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
September sees the average temperatures in the 65°F (18.3°C) to 76°F (24.4°C), and the warm days are an extension of the summer season. The heat can rise above 80°F (26.7°C) on a few days, while most are above 60°F (15.6°C). Nights are comfortable, but there is a rare chance of the temperature dropping below 55°F (12.8°C).
September is usually dry, and the month has a history of high temperatures, including the record high of 111°F (43.9°C). Expect ample sunshine with a mild breeze in the evening, but wear sun protection when the sun is intense during midday.

What is the temperature in September in San Diego?

In San Diego, California, in September, the average high-temperature is 75.9°F (24.4°C), and the average low-temperature is 65.1°F (18.4°C).

How much does it rain in San Diego in September?

In San Diego, in September, it is raining for 1.2 days, with typically 0.2" (4mm) of accumulated precipitation.
Average temperature in September - San Diego, CA
  • Average high temperature in September: 75.9°F

The warmest month (with the highest average high temperature) is August (76.4°F).
The month with the lowest average high temperature is December (64.7°F).

  • Average low temperature in September: 65.2°F

The month with the highest average low temperature is August (66.7°F).
The coldest month (with the lowest average low temperature) is December (48.4°F).

Average humidity in September - San Diego, CA
  • Average humidity in September: 72.7%

The month with the highest relative humidity is July (74.6%).
The month with the lowest relative humidity is January (63.1%).

Average rainfall in September - San Diego, CA
  • Average rainfall in September: 0.2"

The wettest month (with the highest rainfall) is January (2.1").
The driest month (with the lowest rainfall) is July (0").

Average rainfall days in September - San Diego, CA
  • Average rainfall days in September: 1.2 days

The month with the highest number of rainy days is February (7.1 days).
The month with the lowest number of rainy days is August (0.4 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: 8.4h

The month with most sunshine is July (Average sunshine: 9.8h).
The month with least sunshine is December (Average sunshine: 7.5h).

Average UV index in September - San Diego, CA
  • Average UV index in September: 8

Months with the highest UV index are June, July and August (UV index 10).
Months with the lowest UV index are January and December (UV index 3).

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