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September Weather in San Isidro, Puerto Rico

Last updated: August 31, 2025

In September, the average temperature in San Isidro, Puerto Rico hovers around 28°C (82°F), making it a warm destination. Temperatures can dip to a minimum of 24°C (76°F) and can reach a comfortable maximum of 32°C (90°F). However, be prepared for some rain, as the area experiences an average precipitation of 173 mm (6.8 in) over approximately 23 days. With an average humidity of 79%, those venturing here should be ready for a humid yet vibrant atmosphere.

September Temperature in San Isidro

In September in San Isidro, the average temperature is 28°C (82°F). Maximums can reach 32°C (90°F), while minimums can drop to as low as 24°C (76°F). This pleasant climate makes it an ideal destination for travelers seeking warmth and sunshine.

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

The chart illustrates September temperature patterns in San Isidro, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Isidro, September typically has an average temperature of 28°C (82°F), with highs reaching up to 32°C (90°F) and lows dropping to around 24°C (76°F).
JanFebMarAprMayJunJulAugSepOctNovDec777677788081828282817978
Data source: Temperature data for San Isidro 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 Isidro

In San Isidro in September, the precipitation amount is 173 mm (6.8 in) over the course of 23 days.

September Precipitation Trends in San Isidro

The chart displays monthly precipitation patterns in San Isidro, 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 Isidro, September typically receives around 173 mm (6.8 inches) of precipitation spread over approximately 23 days.
JanFebMarAprMayJunJulAugSepOctNovDec394367566468879917314510651
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Isidro

In San Isidro in September humidity is 79%. With an average temperature of 28°C (82°F), this humidity feels like a warm blanket wrapping around you, making outdoor exploration more strenuous and requiring frequent breaks for hydration.

September Average Humidity in San Isidro

This chart illustrates the average monthly humidity levels in San Isidro, 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 Isidro 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 Isidro

In San Isidro 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 Isidro.

Maximum UV Index Levels in San Isidro for September

The chart shows the monthly maximum UV Index (UVI) for San Isidro 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 Isidro typically reaches 13, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec911131314131213131298
Data source: San Isidro 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 Isidro Compares to Other Months

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

This table compares monthly weather conditions in San Isidro, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather25°C (77°F)38 mm (1.5 inches)76%very high
February Weather25°C (77°F)43 mm (1.7 inches)75%extreme
March Weather25°C (77°F)67 mm (2.6 inches)74%extreme
April Weather26°C (78°F)56 mm (2.2 inches)75%extreme
May Weather27°C (80°F)64 mm (2.5 inches)75%extreme
June Weather27°C (81°F)68 mm (2.7 inches)77%extreme
July Weather28°C (82°F)87 mm (3.4 inches)80%extreme
August Weather28°C (82°F)99 mm (3.9 inches)80%extreme
September Weather28°C (82°F)173 mm (6.8 inches)79%extreme
October Weather27°C (81°F)145 mm (5.7 inches)78%extreme
November Weather26°C (80°F)106 mm (4.2 inches)78%very high
December Weather26°C (78°F)51 mm (2.0 inches)76%very high

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