Climate averages 1991–2020
San Antonio weather
in September.
A hot, moderately wet month: the 4th warmest and the 8th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a hot month in San Antonio: daytime highs average 31.6°C and nights cool to about 22.0°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 77 mm of rain on roughly 9 days, which makes September a moderately wet month (the 8th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 22 min on an average September day.
The nearest other city in this atlas is New Braunfels (47 km away). In September its highs average 31.3°C, about as warm as San Antonio, with 74 mm of rain.
Among the 498 cities listed in the United States, San Antonio ranks joint 36th of 498 for the warmest September highs and joint 259th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; San Antonio is 4.7°C warmer than that mean.
From September to October, average highs fall by 4.3°C to 27.3°C, and monthly rainfall rises from 77 mm to 83 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 Antonio climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 16.9°C6.7°C | 6.7°C | 57 | 7.2 | 10.510 h |
| February | 19.3°C8.7°C | 8.7°C | 59 | 7.5 | 11.111 h |
| March | 22.8°C12.1°C | 12.1°C | 79 | 9.2 | 12.012 h |
| April | 26.6°C15.7°C | 15.7°C | 78 | 8.5 | 12.913 h |
| May | 29.9°C19.9°C | 19.9°C | 103 | 11.2 | 13.614 h |
| June | 33.0°C23.1°C | 23.1°C | 69 | 9.5 | 14.014 h |
| July | 34.5°C24.1°C | 24.1°C | 50 | 6.1 | 13.814 h |
| August | 35.1°C24.7°C | 24.7°C | 50 | 5.8 | 13.213 h |
| September, selected | 31.6°C22.0°C | 22.0°C | 77 | 8.6 | 12.412 h |
| October | 27.3°C17.3°C | 17.3°C | 83 | 7.7 | 11.511 h |
| November | 21.5°C11.7°C | 11.7°C | 67 | 7.2 | 10.711 h |
| December | 17.5°C7.8°C | 7.8°C | 63 | 7.5 | 10.310 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
- New Braunfels in SeptemberUnited States · 47 kmHigh 31.3°C · Low 21.8°C · 74 mm rain
- Austin in SeptemberUnited States · 118 kmHigh 31.3°C · Low 21.8°C · 75 mm rain
- Round Rock in SeptemberUnited States · 144 kmHigh 31.1°C · Low 21.5°C · 74 mm rain
- Killeen in SeptemberUnited States · 202 kmHigh 30.8°C · Low 21.3°C · 69 mm rain
- Corpus Christi in SeptemberUnited States · 210 kmHigh 30.7°C · Low 23.8°C · 113 mm rain
- Piedras Negras in SeptemberMexico · 213 kmHigh 32.8°C · Low 23.2°C · 79 mm rain
- Temple in SeptemberUnited States · 216 kmHigh 31.0°C · Low 21.4°C · 69 mm rain
- Ciudad Acuña in SeptemberMexico · 238 kmHigh 32.3°C · Low 22.8°C · 65 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 Antonio) is explained once on the San Antonio year overview and on the Sources, method and limits page.