San Diego weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Excellent
Best time to visit: July – September
What is the weather like in San Diego in September?
In September, San Diego is warm: daytime highs average 25 °C, and nights cool down to about 18 °C. The sea averages 20.6 °C – refreshing for a swim. With around 10 hours of sunshine a day, there is plenty of sun. It hardly ever rains. All in all, September is an excellent month for a holiday in San Diego.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 89 | 88 | 72 |
| Day | 26° | 25° | 23° |
| Night | 18° | 18° | 15° |
| Sea | 21° | 21° | 19° |
| Sun | 12 h | 10 h | 9 h |
| Rain days | 0 | 1 | 2 |
More details for September
- Daylight
- 12 h 25 min06:31 – 18:57
- UV index
- 8 · very highclear sky, noon (estimate)
- Muggy days
- 9 daysdew point 18 °C or more
- Wind
- 16 km/haverage daily peak
- Cloud cover
- 29 %on average
- Hot days
- 2 days30 °C or more
- Time zone
- UTC−7America/Los_Angeles
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %51 %
- Sunshineweight 20 %100 %
- Few rainy daysweight 20 %100 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
San Diego in September: quick answers
Is San Diego hot in September?
Warm rather than hot: in September, daytime highs in San Diego average 25 °C and nights cool to about 18 °C. On about 2 days the thermometer climbs to 30 °C or more.
Can you swim in San Diego in September?
Yes. In September the sea averages 20.6 °C – refreshing for a swim.
Does it rain much in San Diego in September?
It hardly ever rains.
San Diego month by month
The whole year in San DiegoAll destinations: USA
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, GeoNames (CC BY 4.0)