Last updated: August 27, 2025
In September, the average temperature in San Antonio, Mexico hovers around 18°C (65°F), with a minimum of 7°C (46°F) and a pleasant maximum reaching 29°C (85°F). Expect some rain, as 121 mm (4.8 in) of precipitation falls over 17 days, contributing to an average humidity of 81%. Prepare for a mix of warmth and moisture in this vibrant season!
In September in San Antonio, the average temperature is 18°C (65°F). Maximums can reach 29°C (85°F), while minimums can drop to as low as 7°C (46°F). This mild climate makes San Antonio a comfortable destination for travelers looking to enjoy outdoor activities and explore the local sights.
In San Antonio in September, the total precipitation amount is 121 mm (4.8 in) recorded over the course of 17 days.
In San Antonio in September, humidity is 81%. With an average temperature of 18°C (65°F), this humidity feels like a thick blanket wrapping around you, making every step feel heavier and the air thick and sultry—a challenging environment for traveling.
In San Antonio in September, the maximum UV index is 14, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, so it's crucial to take precautions. For the detailed hourly UV index in San Antonio, you can check here.
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 | 13°C (55°F) | 7 mm (0.3 inches) | 74% | very high |
| February Weather | 15°C (60°F) | 10 mm (0.4 inches) | 65% | extreme |
| March Weather | 18°C (64°F) | 14 mm (0.5 inches) | 58% | extreme |
| April Weather | 20°C (68°F) | 9 mm (0.4 inches) | 58% | extreme |
| May Weather | 21°C (71°F) | 45 mm (1.8 inches) | 67% | extreme |
| June Weather | 20°C (68°F) | 120 mm (4.7 inches) | 76% | extreme |
| July Weather | 19°C (67°F) | 106 mm (4.2 inches) | 67% | extreme |
| August Weather | 20°C (67°F) | 77 mm (3.0 inches) | 68% | extreme |
| September Weather | 18°C (65°F) | 121 mm (4.8 inches) | 81% | extreme |
| October Weather | 17°C (63°F) | 63 mm (2.5 inches) | 83% | extreme |
| November Weather | 15°C (58°F) | 23 mm (0.9 inches) | 84% | very high |
| December Weather | 13°C (55°F) | 7 mm (0.3 inches) | 81% | very high |