September is one of the warmer months of the year in San Diego, with average highs near 31.1°C and lows around 16.8°C (mean 24°C). It is one of the drier months, averaging 10 mm of rainfall and 50% relative humidity across the period.
September is one of the warmer months of the year in San Diego. Across 45 years of records, the warmest September in San Diego was 2020 — when the month averaged 26.9°C — while the coldest was 1986 at 19.6°C. Typical September days reach 31.1°C with nights near 16.8°C. The long-term trend is warming, about 0.3°C per decade.
September is one of the drier months in San Diego, averaging 10 mm of rainfall. The wettest September on record was 1997 with 48 mm, while the driest were 1993 and 2020 at 0 mm.
Relative humidity in San Diego during September averages 50%. The most humid September was 2023 at 66%, and the least humid was 2020 at 36%.
September receives about 5.3 kWh/m²/day of solar energy in San Diego. The sunniest September was 2014 at 6 kWh/m²/day, and the cloudiest was 2011 at 4.4.
Average wind speed in San Diego during September is 2 m/s. The windiest September was 1986 at 2.6 m/s, while the calmest was 2020 at 1.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 23.2°C | 23.9°C | 24.1°C | 24.3°C | 24.5°C | +1.3°C |
| Avg High | 30.2°C | 31.0°C | 31.5°C | 31.3°C | 31.5°C | +1.3°C |
| Avg Low | 16.2°C | 16.8°C | 16.8°C | 17.2°C | 17.6°C | +1.4°C |
| Avg Rain | 15 mm | 9 mm | 6 mm | 9 mm | 11 mm | -4 mm |
September temperatures in San Diego have risen by about 0.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 8.8°C (2019) to a record high of 43.8°C (2020).
Rainfall in September is one of the drier months, averaging 10 mm, with a wettest year of 48 mm.
One of the best times to visit San Diego
September is one of the best times to visit San Diego. Expect days averaging 31.1°C and nights around 16.8°C (mean 24°C) — warmer than San Diego's yearly average — with low rainfall (10 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 30.3°C | 24.0°C | 17.7°C | 36.9°C | 14.0°C | 21 mm | 60% | 2.2 m/s | 5.2 |
| 2024 | 32.2°C | 25.0°C | 17.7°C | 42.8°C | 11.6°C | 1 mm | 48% | 2.1 m/s | 5.3 |
| 2023 | 27.8°C | 21.4°C | 15.0°C | 35.2°C | 11.7°C | 7 mm | 66% | 2.5 m/s | 5 |
| 2022 | 32.0°C | 25.6°C | 19.2°C | 39.8°C | 12.9°C | 29 mm | 56% | 2.1 m/s | 5.5 |
| 2021 | 31.7°C | 24.3°C | 17.0°C | 38.9°C | 12.0°C | 6 mm | 48% | 2 m/s | 5.5 |
| 2020 🔥 | 35.0°C | 26.9°C | 18.9°C | 43.8°C | 14.2°C | 0 mm | 36% | 1.6 m/s | 5.6 |
| 2019 | 30.7°C | 23.8°C | 17.0°C | 37.6°C | 8.8°C | 10 mm | 52% | 2.2 m/s | 5.7 |
| 2018 | 31.9°C | 24.1°C | 16.3°C | 38.3°C | 13.3°C | 0 mm | 47% | 1.8 m/s | 5.1 |
| 2017 | 29.4°C | 23.2°C | 17.0°C | 40.5°C | 10.9°C | 4 mm | 56% | 2.5 m/s | 5.5 |
| 2016 | 29.2°C | 22.5°C | 15.7°C | 36.1°C | 10.9°C | 19 mm | 53% | 2.2 m/s | 5.2 |
| 2015 | 31.5°C | 25.0°C | 18.5°C | 37.9°C | 12.4°C | 27 mm | 58% | 1.9 m/s | 5.7 |
| 2014 | 32.4°C | 25.4°C | 18.4°C | 38.9°C | 13.2°C | 3 mm | 53% | 2.1 m/s | 6 |
| 2013 | 31.1°C | 24.0°C | 16.9°C | 37.3°C | 10.1°C | 14 mm | 49% | 1.9 m/s | 5.6 |
| 2012 | 33.8°C | 26.6°C | 19.3°C | 36.8°C | 13.1°C | 3 mm | 41% | 1.7 m/s | 5.6 |
| 2011 | 31.8°C | 24.2°C | 16.7°C | 38.5°C | 11.7°C | 10 mm | 46% | 1.7 m/s | 4.4 |
| 2010 | 31.5°C | 23.8°C | 16.1°C | 39.7°C | 10.5°C | 4 mm | 44% | 2 m/s | 5 |
| 2009 | 33.1°C | 25.6°C | 18.1°C | 37.9°C | 12.1°C | 3 mm | 42% | 1.8 m/s | 5.5 |
| 2008 | 32.6°C | 25.1°C | 17.6°C | 37.1°C | 11.2°C | 3 mm | 47% | 1.8 m/s | 5.1 |
| 2007 | 29.0°C | 22.4°C | 15.7°C | 40.0°C | 10.0°C | 6 mm | 53% | 2.4 m/s | 5.8 |
| 2006 | 31.3°C | 24.1°C | 16.9°C | 38.8°C | 10.4°C | 4 mm | 44% | 1.8 m/s | 5.6 |
| 2005 | 29.7°C | 22.3°C | 14.9°C | 35.1°C | 10.6°C | 2 mm | 47% | 2.1 m/s | 5.7 |
| 2004 | 30.8°C | 23.6°C | 16.4°C | 38.8°C | 11.1°C | 4 mm | 48% | 2.1 m/s | 5.6 |
| 2003 | 33.3°C | 25.6°C | 17.9°C | 38.7°C | 13.6°C | 4 mm | 48% | 1.7 m/s | 4.8 |
| 2002 | 32.1°C | 24.9°C | 17.6°C | 40.5°C | 12.2°C | 11 mm | 44% | 1.9 m/s | 5 |
| 2001 | 31.7°C | 24.2°C | 16.6°C | 37.8°C | 12.4°C | 5 mm | 48% | 2 m/s | 4.8 |
| 2000 | 30.9°C | 23.4°C | 15.9°C | 38.7°C | 12.1°C | 12 mm | 51% | 2.1 m/s | 5.3 |
| 1999 | 29.9°C | 22.5°C | 15.2°C | 36.4°C | 10.2°C | 11 mm | 53% | 2.1 m/s | 4.6 |
| 1998 | 28.7°C | 22.3°C | 16.0°C | 37.9°C | 11.3°C | 4 mm | 60% | 2.4 m/s | 5.3 |
| 1997 🌧️ | 32.1°C | 25.3°C | 18.6°C | 37.0°C | 13.1°C | 48 mm | 55% | 2 m/s | 5.5 |
| 1996 | 30.0°C | 23.0°C | 15.9°C | 35.1°C | 12.5°C | 2 mm | 56% | 2.2 m/s | 5.1 |
| 1995 | 32.2°C | 25.1°C | 18.0°C | 37.6°C | 12.2°C | 5 mm | 46% | 2 m/s | 5.5 |
| 1994 | 30.4°C | 23.3°C | 16.3°C | 36.3°C | 10.9°C | 0 mm | 50% | 2 m/s | 5.6 |
| 1993 | 31.4°C | 23.8°C | 16.3°C | 38.7°C | 9.2°C | 0 mm | 44% | 2 m/s | 5 |
| 1992 | 32.6°C | 25.0°C | 17.4°C | 36.6°C | 13.4°C | 0 mm | 43% | 1.7 m/s | 5.6 |
| 1991 | 30.9°C | 24.0°C | 17.1°C | 36.0°C | 10.8°C | 12 mm | 54% | 1.7 m/s | 4.6 |
| 1990 | 31.4°C | 24.2°C | 16.9°C | 39.6°C | 12.2°C | 6 mm | 49% | 2 m/s | 5.4 |
| 1989 | 30.9°C | 23.6°C | 16.3°C | 37.3°C | 9.8°C | 9 mm | 43% | 2.1 m/s | 5.6 |
| 1988 | 30.9°C | 23.3°C | 15.7°C | 38.9°C | 10.0°C | 1 mm | 48% | 2.2 m/s | 4.7 |
| 1987 | 30.6°C | 23.4°C | 16.1°C | 38.0°C | 12.0°C | 11 mm | 50% | 2 m/s | 4.7 |
| 1986 ❄️ | 26.3°C | 19.6°C | 12.9°C | 37.2°C | 9.3°C | 29 mm | 57% | 2.6 m/s | 4.9 |
| 1985 | 27.1°C | 20.6°C | 14.1°C | 34.0°C | 10.2°C | 14 mm | 56% | 2.5 m/s | 5.4 |
| 1984 | 33.0°C | 26.1°C | 19.2°C | 38.9°C | 14.1°C | 7 mm | 50% | 2.1 m/s | 5.4 |
| 1983 | 31.6°C | 24.9°C | 18.2°C | 38.4°C | 12.6°C | 23 mm | 53% | 1.9 m/s | — |
| 1982 | 29.3°C | 22.8°C | 16.3°C | 40.0°C | 9.1°C | 29 mm | 56% | 2.2 m/s | — |
| 1981 | 31.8°C | 24.3°C | 16.7°C | 36.4°C | 11.8°C | 11 mm | 43% | 2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 31.1°C with lows near 16.8°C (mean 24°C), based on 45 years of NASA POWER data.
September averages 10 mm of rainfall in San Diego, one of the drier months. The wettest on record was 48 mm in 1997.
The hottest September reached 43.8°C in 2020. The coldest dipped to 8.8°C in 2019.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 0.4°C. Daytime highs moved from 30.6°C to 30.8°C and overnight lows from 16.9°C to 17.3°C over the same span.
September is one of the warmer months of the year in San Diego and one of the drier months, so plan for around 31.1°C daytime highs and 16.8°C at night.
Not quite — September is the 10th coolest month in San Diego, averaging 24°C.
For September in San Diego, pack light, breathable clothing and sun protection, with typical highs of 31.1°C and lows of 16.8°C.
Relative humidity in September averages 50% — relatively dry.
Average wind speed in September is 2 m/s. The windiest September on record averaged 2.6 m/s (1986).
The wettest September on record was 1997 with 48 mm. On average, September sees 10 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in San Diego behaves each September, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for September specifically, along with year-by-year records and how the month has changed over the decades.
