Weather in San Diego in September 2025
- September is usually the hottest month of the year in San Diego;
Average weather
Average temperature in San Diego in September
The temperature in September is +24°C on average, with a range between a maximum of +28°C during the day and a minimum of +17°C at night.
The average maximum temperature goes down 27% by the end of the month, compared with the beginning of the month, from +24°C to +21°C.
Is San Diego warm or cold in September?
San Diego is typically warm in September.
Maximum temperatures go up compared to the previous month from +24°C to +24°C. The minimum temperature also goes up from +19°C to +19°C.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is the hottest month in San Diego, here is the comparison with other months:
Water temperature in San Diego in September
Water in San Diego in September is Fresh. It varies from +18°C to +21°C, with an average of +19°C. This is almost similar to the air temperature, which averages +24°C.
The water temperature in September is one of the warmest of the entire year:
Can you swim in San Diego in September?
Climate in San Diego in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +24°C | +24°C | +23°C | ||||
| Min. temperature | ||||||
| +16°C | +13°C | +9°C | ||||
| Max. temperature | ||||||
| +31°C | +38°C | +36°C | ||||
| Rainfall | ||||||
| 4 mm | 10 mm | 20 mm | ||||
| Wind | ||||||
| 3 m/s | 2 m/s | 2 m/s | ||||
| Avg. water temperature | ||||||
| +20°C | +19°C | +18°C | ||||
| Humidity | ||||||
| 76% | 75% | 71% | ||||
| Air pressure | ||||||
| 1012 HPa | 1011 HPa | 1013 HPa | ||||
| Sunny days | ||||||
| 5 | 6 | 8 | ||||
| Cloudy days | ||||||
| 24 | 20 | 17 | ||||
| Rainy days | ||||||
| 2 | 4 | 6 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as good as in August. The temperature levels stay the same in the area of +24°C for average maximum temperature during the day. Prepare for more rain. Average rainfall goes from 4 mm to 10 mm. It feels drier, as humidity decreases from 76% to 75%. Winds are calmer in comparison to August, going down from 3 m/s to 2 m/s on average. The good news is there are likely to be more sunny days in September, from 5 to 6.
October brings much the same weather, it remains good.
Wind
The average wind speed is 3 m/s getting up to 4 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in San Diego is gradually increasing during September, going from 3 m/s to 3 m/s over the course of the month.
Rain
How was the weather last September in San Diego?
Climate Change over Years
The climate in San Diego in September has not changed much over the last 43 years.
The average temperature was the lowest in 2001 (+19°C) and the highest in 2014 (+23°C). The driest year was 2002 with only 156 mm of rainfall, and the wettest year was 2023 with 1311 mm.
FAQ
Is September a good time to visit San Diego?
Can you sunbathe in San Diego in September?
Can you swim in San Diego in September?
Is San Diego rainy in September?
Is it sunny in San Diego in September?
Other cities in USA
Monthly weather in San Diego
Source of the data
For this page, we’ve looked at the typical weather in San Diego, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.