Last updated: June 24, 2025
In September, the average temperature in San Antonio, United States hovers around a warm 27°C (81°F). Expect a pleasant range, with minimums dropping to 18°C (66°F) and highs reaching up to 35°C (95°F). Be prepared for some rain, as precipitation averages 189 mm (7.4 in) over 20 days, along with a notable average humidity of 83%. Enjoy the tropical vibes!
In September in San Antonio, the average temperature is 27°C (81°F), with maximums reaching up to 35°C (95°F) and minimums dropping as low as 18°C (66°F). It's an ideal time to visit, as you can enjoy warm weather while still having pleasant evenings.
In San Antonio in September, the precipitation amount is 189 mm (7.4 in) over the course of 20 days.
In San Antonio in September humidity is 83%. With an average temperature of 27°C (81°F), this humidity feels like a warm blanket enveloping you, making sightseeing and outdoor activities feel more exhausting and requiring frequent breaks to relax in the shade or cool off.
In San Antonio in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in San Antonio.
UV Risk Categories
Weather in San Antonio varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Antonio, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 16°C (60°F) | 43 mm (1.7 inches) | 83% | high |
| February Weather | 19°C (66°F) | 69 mm (2.7 inches) | 80% | very high |
| March Weather | 20°C (68°F) | 20 mm (0.8 inches) | 75% | very high |
| April Weather | 23°C (73°F) | 77 mm (3.0 inches) | 70% | extreme |
| May Weather | 25°C (78°F) | 123 mm (4.8 inches) | 68% | extreme |
| June Weather | 27°C (81°F) | 223 mm (8.8 inches) | 75% | extreme |
| July Weather | 27°C (81°F) | 276 mm (10.8 inches) | 79% | extreme |
| August Weather | 28°C (82°F) | 247 mm (9.7 inches) | 81% | extreme |
| September Weather | 27°C (81°F) | 189 mm (7.4 inches) | 83% | extreme |
| October Weather | 25°C (77°F) | 82 mm (3.2 inches) | 81% | very high |
| November Weather | 20°C (68°F) | 49 mm (1.9 inches) | 82% | high |
| December Weather | 17°C (64°F) | 70 mm (2.8 inches) | 84% | moderate |