San Diego Weather in September

September carries on the fine summer weather at San Diego, California. Temperatures of over 90 degrees Fahrenheit (32 degrees Celsius) are most likely to happen this month, although it doesn't get that hot here every year.

This page gives detailed information on the typical September temperature, precipitation, sun, humidity, wind and storms for San Diego. The numbers are historical averages based on climate data gathered at the San Diego International Airport, located on San Diego Bay near the city center.

Temperature Weather iconTemperature

77 °F September average high 25 °C
66 °F September average low 19 °C
29 days 70 °F max. or more (21 °C)
27 days 70 °F min. or less (21 °C)

Nearly every day in September warms to over 70 °F (21 °C) in San Diego. The city averages 8 days this month when the thermometer reaches into the 80s °F (over 26 °C). Temperatures above 90 °F (32 °C) occur on average one day per year, and in rare years reach 100 °F (38 °C).

At night, the thermometer dips to 60 °F (16 °C) or below on an average of one day this month. But September does not normally get as cold as 50 °F (10 °C).

Rainy Weather iconRain

0.1 in total precipitation 3 mm
1 day of rain

Most years, San Diego gets less than 0.1 inches (3 mm) of rain in September. About one in every two years, the city receives no rain at all this month.

Sunny Weather iconSun

69 % sunshine
15 days clear skies

The sun's rays reach the ground in San Diego during 69 percent of daylight hours on average in September, for a total of 255 hours in the month. Typically on 15 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in September at San Diego lasts for 12 hours and 20 minutes a day on average. The longest day of the month is the 1st with 12 hours and 49 minutes of daylight. By the end of the month, the days have shortened to 11:52 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

73 % September average humidity

The relative humidity in San Diego during September usually peaks at 80 percent just after midnight then drops to 62 percent by early afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 80 80 77 66 62 65 74 78

Windy Weather iconWind

7.1 mph September wind speed average 11.4 kph

September is an average month in San Diego for wind speed.

Stormy Weather iconStorms

0 days rainfall of 0.5 inches (13 mm) or more
0 days with thunderstorms in September

Just once a decade does San Diego have a day in September when it gets as much as one-half to one inch (13 to 25 mm) of rain.

San Diego has a thunderstorm during September about once in five years.


The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.

San Diego Weather
Back to Top