San Diego Weather in September
San Diego in September sees high temperatures, with highs around 26°C (79°F) and overnight lows of 18°C (64°F). With just 4.3 mm (0.2 in) of rainfall on average, rain is rarely an issue.
Rainfall in San Diego in September
This month experiences about a single day of rain according to historical data, averaging 4.3 mm (0.2 in). If rain does fall, it tends to be a moderate shower rather than anything heavy.
Temperature in San Diego in September
September is one of the better months to visit San Diego. Expect 26°C (79°F) during the day and 18°C (64°F) at night. Overall, the month follows a fairly predictable daily temperature pattern. Nights cool down to 18°C (64°F), so a light jacket or extra layer is useful once the sun goes down. On the plus side, the cooler nights make for comfortable sleeping conditions. This is typically the warmest month of the year, so light summer clothing is a good idea.
Sunshine in San Diego in September
The city usually sees around 253 hours of sunlight, indicating many sunny days — a great month for sightseeing.If your ideal day consists of dry skies and pleasant temperatures, January, February, March, April, May, June, July, August, September, October and November typically offer the best circumstances for San Diego.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our San Diego's climate page.
San Diego Temperature in September
Min Temperature
18°C (64°F)
Max Temperature
26°C (79°F)
Chance of Rain
3%
Precipitation
4.3 mm (0.2 in)
Rainy days
a single day
Humidity
74%
Sunshine
253 hours
Percentage Sunshine
68%
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in San Diego typically stay consistent throughout September, with daily highs averaging around 26°C (79°F). Nights are pleasant, with lows typically ranging from 18°C (64°F) to 20°C (68°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for San Diego in September
Browse day-by-day weather records for San Diego spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
San Diego historical weather extremes in September
According to our 49 years of weather records for San Diego, the following extremes were recorded between 1976 and 2025.
- The hottest September day on record in San Diego reached 38°C (100°F) (September 26, 2016).
- On September 26, 1999, San Diego saw its coldest September day with temperatures maxing out at 19°C (66°F).
- The coldest night in September in San Diego was on September 20, 1989, with a minimum of 14°C (57°F).
Best Places in the United States of America in September
Find out more about the weather in the United States of America and which places have the best travel conditions in this month. See all of the United States of America in September →
perfect weather
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unpleasant
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What to Wear in San Diego in September
Warm temperatures in September make for comfortable sightseeing weather. Pack breathable fabrics like cotton shirts, knee-length shorts or skirts, and comfortable walking shoes. A thin long sleeve for indoor spaces is handy. With minimal rainfall expected, you can leave the rain gear at home. Don't forget sun protection, sunglasses, sunscreen, and a hat. These are all good ideas with this much sunshine.What To Do in San Diego in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our San Diego's climate page.
Temperature Rainfall Sunshine Humidity
See the full San Diego climate overview or explore weather in the United States of America.
