September is one of the warmer months of the year in San Antonio, with average highs near 32.8°C and lows around 20.8°C (mean 26.8°C). It is a relatively wet time of year, averaging 76 mm of rainfall and 65% relative humidity across the period.
September is one of the warmer months of the year in San Antonio. Across 45 years of records, the warmest September in San Antonio was 2023 — when the month averaged 31.2°C — while the coldest was 2001 at 24.1°C. Typical September days reach 32.8°C with nights near 20.8°C. The long-term trend is warming, about 0.5°C per decade.
September is a relatively wet time of year in San Antonio, averaging 76 mm of rainfall. The wettest September on record was 2018 with 248 mm, while the driest was 2008 at 11 mm.
Relative humidity in San Antonio during September averages 65%. The most humid September was 2018 at 82%, and the least humid was 2011 at 45%.
September receives about 5.3 kWh/m²/day of solar energy in San Antonio. The sunniest September was 2011 at 6.1 kWh/m²/day, and the cloudiest was 2018 at 4.2.
Average wind speed in San Antonio during September is 2.5 m/s. The windiest September was 1984 at 3.2 m/s, while the calmest were 1996, 2022 and 2025, among others at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 26.4°C | 26.4°C | 26.0°C | 27.2°C | 28.5°C | +2.1°C |
| Avg High | 32.6°C | 32.4°C | 31.8°C | 33.0°C | 35.1°C | +2.5°C |
| Avg Low | 20.2°C | 20.5°C | 20.3°C | 21.5°C | 21.9°C | +1.7°C |
| Avg Rain | 66 mm | 71 mm | 81 mm | 104 mm | 46 mm | -20 mm |
September temperatures in San Antonio have risen by about 3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 8°C (1985) to a record high of 44.8°C (2000).
Rainfall in September is a relatively wet time of year, averaging 76 mm, with a wettest year of 248 mm.
A good time to visit San Antonio
September is a good time to visit San Antonio, with days averaging 32.8°C and nights around 20.8°C (mean 26.8°C, warmer than San Antonio's yearly average) and moderate rainfall. April and October are marginally more temperate, but September still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 35.7°C | 28.8°C | 21.9°C | 39.8°C | 18.5°C | 28 mm | 53% | 1.9 m/s | 5.7 |
| 2024 | 35.8°C | 28.9°C | 22.1°C | 38.3°C | 16.0°C | 30 mm | 56% | 2.6 m/s | 5.5 |
| 2023 🔥 | 38.1°C | 31.2°C | 24.3°C | 42.3°C | 22.1°C | 18 mm | 53% | 2.3 m/s | 5.8 |
| 2022 | 35.0°C | 28.3°C | 21.5°C | 37.6°C | 16.7°C | 22 mm | 60% | 1.9 m/s | 5.8 |
| 2021 | 35.2°C | 28.4°C | 21.6°C | 39.0°C | 14.7°C | 71 mm | 57% | 2.2 m/s | 5.9 |
| 2020 | 30.8°C | 25.4°C | 20.0°C | 35.0°C | 11.6°C | 105 mm | 70% | 2.9 m/s | 4.7 |
| 2019 | 37.0°C | 30.5°C | 24.0°C | 39.3°C | 22.0°C | 27 mm | 58% | 2.9 m/s | 5.7 |
| 2018 🌧️ | 29.5°C | 25.6°C | 21.6°C | 38.0°C | 15.8°C | 248 mm | 82% | 2.3 m/s | 4.2 |
| 2017 | 31.7°C | 25.9°C | 20.2°C | 36.1°C | 14.7°C | 84 mm | 70% | 2.6 m/s | 5.4 |
| 2016 | 31.5°C | 26.5°C | 21.5°C | 35.5°C | 14.5°C | 91 mm | 76% | 2.2 m/s | 5.5 |
| 2015 | 35.2°C | 28.8°C | 22.5°C | 39.1°C | 17.2°C | 24 mm | 59% | 2.4 m/s | 5.6 |
| 2014 | 32.2°C | 26.8°C | 21.5°C | 37.6°C | 16.1°C | 91 mm | 71% | 2.5 m/s | 4.9 |
| 2013 | 33.0°C | 27.2°C | 21.5°C | 38.3°C | 14.5°C | 113 mm | 67% | 2.4 m/s | 5.2 |
| 2012 | 32.6°C | 26.4°C | 20.1°C | 39.7°C | 15.4°C | 137 mm | 64% | 2.5 m/s | 5.6 |
| 2011 | 36.4°C | 28.8°C | 21.3°C | 40.6°C | 16.9°C | 32 mm | 45% | 2.5 m/s | 6.1 |
| 2010 | 30.7°C | 25.9°C | 21.1°C | 35.7°C | 11.9°C | 192 mm | 76% | 2.5 m/s | 5 |
| 2009 | 30.0°C | 25.1°C | 20.1°C | 36.8°C | 14.0°C | 134 mm | 73% | 2.4 m/s | 4.3 |
| 2008 | 32.8°C | 26.1°C | 19.5°C | 37.8°C | 15.4°C | 11 mm | 59% | 2.3 m/s | 5.7 |
| 2007 | 29.8°C | 25.3°C | 20.8°C | 32.2°C | 17.7°C | 50 mm | 81% | 2 m/s | 5.1 |
| 2006 | 32.1°C | 26.2°C | 20.3°C | 37.7°C | 14.9°C | 86 mm | 64% | 2.5 m/s | 5.1 |
| 2005 | 36.1°C | 29.7°C | 23.3°C | 42.2°C | 20.7°C | 38 mm | 59% | 2.4 m/s | 5.6 |
| 2004 | 32.9°C | 26.8°C | 20.7°C | 35.8°C | 16.5°C | 49 mm | 64% | 2.2 m/s | 5 |
| 2003 | 29.5°C | 24.4°C | 19.4°C | 34.3°C | 13.4°C | 153 mm | 76% | 2.2 m/s | 4.7 |
| 2002 | 30.2°C | 24.8°C | 19.5°C | 35.6°C | 13.6°C | 155 mm | 72% | 2.7 m/s | 5.1 |
| 2001 ❄️ | 29.2°C | 24.1°C | 19.1°C | 32.5°C | 10.5°C | 86 mm | 77% | 2.2 m/s | 5.7 |
| 2000 | 35.0°C | 27.7°C | 20.3°C | 44.8°C | 9.2°C | 44 mm | 52% | 2.7 m/s | 5.9 |
| 1999 | 35.1°C | 28.0°C | 20.9°C | 40.1°C | 13.5°C | 14 mm | 50% | 2.7 m/s | 5.9 |
| 1998 | 31.9°C | 27.1°C | 22.2°C | 35.6°C | 19.1°C | 90 mm | 75% | 2.4 m/s | 5.1 |
| 1997 | 35.1°C | 28.4°C | 21.7°C | 38.6°C | 15.6°C | 44 mm | 60% | 2.5 m/s | 5.6 |
| 1996 | 29.7°C | 24.8°C | 19.9°C | 33.6°C | 10.4°C | 118 mm | 78% | 1.9 m/s | 5.3 |
| 1995 | 32.8°C | 26.6°C | 20.4°C | 38.1°C | 9.3°C | 82 mm | 67% | 2.2 m/s | 5.5 |
| 1994 | 31.0°C | 24.7°C | 18.4°C | 36.8°C | 9.2°C | 88 mm | 66% | 2.2 m/s | 5.3 |
| 1993 | 33.9°C | 27.2°C | 20.4°C | 37.3°C | 13.6°C | 34 mm | 56% | 2.6 m/s | 5.4 |
| 1992 | 33.6°C | 27.2°C | 20.8°C | 38.1°C | 12.1°C | 44 mm | 62% | 2.9 m/s | 5.5 |
| 1991 | 29.7°C | 24.5°C | 19.3°C | 33.4°C | 11.5°C | 119 mm | 74% | 2.4 m/s | 4.7 |
| 1990 | 31.1°C | 25.9°C | 20.7°C | 35.8°C | 12.7°C | 77 mm | 71% | 1.9 m/s | 5.1 |
| 1989 | 33.3°C | 26.1°C | 18.8°C | 38.2°C | 11.2°C | 22 mm | 51% | 2.7 m/s | 5.9 |
| 1988 | 34.1°C | 27.6°C | 21.1°C | 38.6°C | 15.4°C | 59 mm | 59% | 3 m/s | 5 |
| 1987 | 32.5°C | 26.2°C | 19.9°C | 36.8°C | 13.8°C | 54 mm | 65% | 2.3 m/s | 5.6 |
| 1986 | 31.5°C | 26.9°C | 22.3°C | 34.5°C | 20.0°C | 104 mm | 76% | 3 m/s | 5 |
| 1985 | 32.4°C | 26.4°C | 20.5°C | 40.4°C | 8.0°C | 131 mm | 65% | 3.1 m/s | 5.2 |
| 1984 | 32.2°C | 25.7°C | 19.3°C | 36.9°C | 9.0°C | 37 mm | 59% | 3.2 m/s | 5.1 |
| 1983 | 31.7°C | 25.8°C | 19.9°C | 37.9°C | 8.4°C | 95 mm | 68% | 2.8 m/s | — |
| 1982 | 34.0°C | 27.3°C | 20.6°C | 38.3°C | 13.4°C | 48 mm | 59% | 2.5 m/s | — |
| 1981 | 31.4°C | 25.5°C | 19.6°C | 34.0°C | 11.7°C | 43 mm | 70% | 2.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 32.8°C with lows near 20.8°C (mean 26.8°C), based on 45 years of NASA POWER data.
September averages 76 mm of rainfall in San Antonio, a relatively wet time of year. The wettest on record was 248 mm in 2018.
The hottest September reached 44.8°C in 2000. The coldest dipped to 8°C in 1985.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 3°C. Daytime highs moved from 32.3°C to 36°C and overnight lows from 20°C to 22.3°C over the same span.
September is one of the warmer months of the year in San Antonio and a relatively wet time of year, so plan for around 32.8°C daytime highs and 20.8°C at night.
Not quite — September is the 9th coolest month in San Antonio, averaging 26.8°C.
For September in San Antonio, pack light, breathable clothing and sun protection, with typical highs of 32.8°C and lows of 20.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 65% — moderately humid.
Average wind speed in September is 2.5 m/s. The windiest September on record averaged 3.2 m/s (1984).
The wettest September on record was 2018 with 248 mm. On average, September sees 76 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 Antonio 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.
