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September Weather in San Antonio, Puerto Rico

Last updated: August 31, 2025

In San Antonio, Puerto Rico, the average temperature in September hovers around 27°C (81°F). You'll experience pleasant warmth, with minimums dipping to 25°C (77°F) and maximums reaching up to 31°C (88°F). However, be prepared for some rain, as 188 mm (7.4 in) may fall over the course of 23 days. The air is quite humid, with an average humidity of 79%, making it essential to stay refreshed!

September Temperature in San Antonio

In September in San Antonio, the average temperature is 27°C (81°F). Maximums can reach 31°C (88°F), while minimums can be as low as 25°C (77°F). This mild and warm climate makes it an ideal destination for travelers seeking pleasant weather.

September Weather in San Antonio: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in San Antonio, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Antonio, September typically has an average temperature of 27°C (81°F), with highs reaching up to 31°C (88°F) and lows dropping to around 25°C (77°F).
JanFebMarAprMayJunJulAugSepOctNovDec767676777980818181807978
Data source: Temperature data for San Antonio generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in San Antonio

In San Antonio in September, the precipitation amount is 188 mm (7.4 in) distributed over a span of 23 days.

September Precipitation Trends in San Antonio

The chart displays monthly precipitation patterns in San Antonio, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In San Antonio, September typically receives around 188 mm (7.4 inches) of precipitation spread over approximately 23 days.
JanFebMarAprMayJunJulAugSepOctNovDec34397266978591971881279943
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Antonio

In San Antonio in September, humidity is 79%. With an average temperature of 27°C (81°F), this humidity feels like a warm and sticky embrace, making travel both challenging and invigorating as the air clings to your skin, urging you to seek shade or a refreshing drink.

September Average Humidity in San Antonio

This chart illustrates the average monthly humidity levels in San Antonio, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in San Antonio is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%75%74%75%75%77%80%80%79%78%78%76%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Antonio

In San Antonio in September, the maximum UV index reaches 13, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's crucial to take protective measures. For detailed information, you can check the Hourly UV Index in San Antonio.

Maximum UV Index Levels in San Antonio for September

The chart shows the monthly maximum UV Index (UVI) for San Antonio in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in San Antonio typically reaches 13, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec911131314131313131298
Data source: San Antonio September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in San Antonio Compares to Other Months

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.

This table compares monthly weather conditions in San Antonio, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather25°C (77°F)34 mm (1.3 inches)76%very high
February Weather25°C (76°F)39 mm (1.5 inches)75%extreme
March Weather25°C (76°F)72 mm (2.8 inches)74%extreme
April Weather25°C (78°F)66 mm (2.6 inches)75%extreme
May Weather26°C (79°F)97 mm (3.8 inches)75%extreme
June Weather27°C (81°F)85 mm (3.3 inches)77%extreme
July Weather27°C (81°F)91 mm (3.6 inches)80%extreme
August Weather27°C (82°F)97 mm (3.8 inches)80%extreme
September Weather27°C (81°F)188 mm (7.4 inches)79%extreme
October Weather27°C (81°F)127 mm (5.0 inches)78%extreme
November Weather26°C (79°F)99 mm (3.9 inches)78%very high
December Weather25°C (78°F)43 mm (1.7 inches)76%very high

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