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September Weather in San Marcos, Mexico

Last updated: August 27, 2025

In September, the average temperature in San Marcos, Mexico hovers around 18°C (65°F), with a minimum of 11°C (51°F) and a maximum reaching 30°C (85°F). Expect 125 mm (4.9 in) of precipitation spread over 18 days, contributing to an average humidity of 82%. Prepare for a blend of mild warmth and occasional showers!

September Temperature in San Marcos

In September in San Marcos, the average temperature is 18°C (65°F), with maximums reaching 30°C (85°F) and minimums dropping to as low as 11°C (51°F). It's a perfect time for travelers to enjoy mild weather while exploring all that San Marcos has to offer.

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

The chart illustrates September temperature patterns in San Marcos, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Marcos, September typically has an average temperature of 18°C (65°F), with highs reaching up to 30°C (85°F) and lows dropping to around 11°C (51°F).
JanFebMarAprMayJunJulAugSepOctNovDec545864687272696965645954
Data source: Temperature data for San Marcos 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 Marcos

In San Marcos in September, the precipitation amount is 125 mm (4.9 in) spread over 18 days.

September Precipitation Trends in San Marcos

The chart displays monthly precipitation patterns in San Marcos, 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 Marcos, September typically receives around 125 mm (4.9 inches) of precipitation spread over approximately 18 days.
JanFebMarAprMayJunJulAugSepOctNovDec121011915521366712543109
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Marcos

In San Marcos in September, humidity is 82%. With an average temperature of 18°C (65°F), this humidity feels like a warm, sticky embrace that can quickly leave travelers feeling fatigued and in need of frequent breaks to stay refreshed and hydrated.

September Average Humidity in San Marcos

This chart illustrates the average monthly humidity levels in San Marcos, 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 Marcos is approximately 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec70%62%53%48%52%64%73%71%82%83%82%84%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Marcos

In San Marcos 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 Marcos.

Maximum UV Index Levels in San Marcos for September

The chart shows the monthly maximum UV Index (UVI) for San Marcos 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 Marcos typically reaches 13, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec811131414141414131297
Data source: San Marcos 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 Marcos Compares to Other Months

Weather in San Marcos varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Marcos, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in San Marcos, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather12°C (54°F)12 mm (0.5 inches)70%very high
February Weather15°C (59°F)10 mm (0.4 inches)62%extreme
March Weather18°C (64°F)11 mm (0.4 inches)53%extreme
April Weather20°C (68°F)9 mm (0.4 inches)48%extreme
May Weather22°C (73°F)15 mm (0.6 inches)52%extreme
June Weather22°C (73°F)52 mm (2.1 inches)64%extreme
July Weather20°C (69°F)136 mm (5.4 inches)73%extreme
August Weather21°C (70°F)67 mm (2.6 inches)71%extreme
September Weather18°C (65°F)125 mm (4.9 inches)82%extreme
October Weather18°C (64°F)43 mm (1.7 inches)83%extreme
November Weather15°C (59°F)10 mm (0.4 inches)82%very high
December Weather12°C (55°F)9 mm (0.3 inches)84%high

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