Climate averages 1991–2020
San Diego weather
in September.
A warm, very dry month: the 2nd warmest and the 4th driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in San Diego: daytime highs average 25.1°C and nights cool to about 17.5°C. By daytime temperature it is the 2nd warmest of the 12 months.
Expect about 2.9 mm of rain on fewer than one day, which makes September a very dry month (the 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 24 min on an average September day.
The nearest other city in this atlas is Chula Vista (11 km away). In September its highs average 24.2°C, 0.9°C cooler than San Diego, with 4.4 mm of rain.
Among the 498 cities listed in the United States, San Diego ranks joint 310th of 498 for the warmest September highs and 38th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; San Diego is 1.8°C cooler than that mean.
From September to October, average highs fall by 2.1°C to 23.0°C, and monthly rainfall rises from 2.9 mm to 12 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
San Diego climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 17.4°C8.7°C | 8.7°C | 50 | 5.5 | 10.310 h |
| February | 17.2°C9.2°C | 9.2°C | 63 | 6.1 | 11.011 h |
| March | 17.8°C10.4°C | 10.4°C | 38 | 5.2 | 12.012 h |
| April | 19.1°C11.9°C | 11.9°C | 16 | 2.9 | 13.013 h |
| May | 20.2°C13.6°C | 13.6°C | 7.1 | 1.6 | 13.814 h |
| June | 22.0°C14.9°C | 14.9°C | 1.2 | 0.2 | 14.314 h |
| July | 24.3°C17.1°C | 17.1°C | 1.3 | 0.3 | 14.114 h |
| August | 25.4°C18.0°C | 18.0°C | 0.4 | 0.1 | 13.413 h |
| September, selected | 25.1°C17.5°C | 17.5°C | 2.9 | 0.6 | 12.412 h |
| October | 23.0°C15.2°C | 15.2°C | 12 | 2.0 | 11.411 h |
| November | 20.3°C11.7°C | 11.7°C | 19 | 2.9 | 10.511 h |
| December | 17.3°C8.8°C | 8.8°C | 40 | 4.9 | 10.010 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Chula Vista in SeptemberUnited States · 11 kmHigh 24.2°C · Low 17.6°C · 4.4 mm rain
- El Cajon in SeptemberUnited States · 21 kmHigh 27.6°C · Low 17.8°C · 4.4 mm rain
- Tijuana in SeptemberMexico · 28 kmHigh 24.4°C · Low 17.9°C · 4.0 mm rain
- Rosarito in SeptemberMexico · 41 kmHigh 24.5°C · Low 18.5°C · 3.1 mm rain
- Escondido in SeptemberUnited States · 45 kmHigh 28.1°C · Low 17.5°C · 5.1 mm rain
- San Marcos in SeptemberUnited States · 48 kmHigh 26.2°C · Low 17.3°C · 3.9 mm rain
- Vista in SeptemberUnited States · 54 kmHigh 28.0°C · Low 18.1°C · 3.9 mm rain
- Oceanside in SeptemberUnited States · 57 kmHigh 25.3°C · Low 18.4°C · 3.3 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for San Diego) is explained once on the San Diego year overview and on the Sources, method and limits page.