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September Weather in Mercedes, Costa Rica

Last updated: August 23, 2025

In September, the average temperature in Mercedes, Costa Rica hovers around 20°C (68°F). Expect a minimum of 15°C (59°F) and a comfortable maximum of 27°C (80°F). However, be prepared for some wet days, as precipitation totals can reach 536 mm (21.1 in) over the course of 30 days, with an average humidity level of 81%.

September Temperature in Mercedes

In September in Mercedes, the average temperature is 20°C (68°F). Maximum temperatures can reach 27°C (80°F), while minimums can drop as low as 15°C (59°F). This mild climate makes Mercedes an ideal destination for travelers seeking comfortable weather conditions.

September Weather in Mercedes: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Mercedes, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mercedes, September typically has an average temperature of 20°C (68°F), with highs reaching up to 27°C (80°F) and lows dropping to around 15°C (59°F).
JanFebMarAprMayJunJulAugSepOctNovDec676868696969686868676767
Data source: Temperature data for Mercedes 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 Mercedes

In Mercedes in September, the total precipitation amount is 536 mm (21.1 in) over a span of 30 days.

September Precipitation Trends in Mercedes

The chart displays monthly precipitation patterns in Mercedes, 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 Mercedes, September typically receives around 536 mm (21.1 inches) of precipitation spread over approximately 30 days.
JanFebMarAprMayJunJulAugSepOctNovDec894557251609568477589536802620191
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mercedes

In Mercedes in September humidity is 81%. With an average temperature of 20°C (68°F), this humidity feels like a warm embrace that can make outdoor activities feel steamy and exhausting, potentially leading travelers to seek shade or a refreshing drink more often.

September Average Humidity in Mercedes

This chart illustrates the average monthly humidity levels in Mercedes, 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 Mercedes is approximately 81%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec68%68%66%67%69%84%85%82%81%80%80%73%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mercedes

In Mercedes 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 Mercedes, you can check here.

Maximum UV Index Levels in Mercedes for September

The chart shows the monthly maximum UV Index (UVI) for Mercedes 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 Mercedes typically reaches 14, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec121415151514141414141211
Data source: Mercedes 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 Mercedes Compares to Other Months

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

This table compares monthly weather conditions in Mercedes, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather19°C (67°F)89 mm (3.5 inches)68%extreme
February Weather20°C (68°F)44 mm (1.8 inches)68%extreme
March Weather20°C (68°F)57 mm (2.3 inches)66%extreme
April Weather20°C (69°F)251 mm (9.9 inches)67%extreme
May Weather20°C (69°F)609 mm (24.0 inches)69%extreme
June Weather20°C (69°F)568 mm (22.4 inches)84%extreme
July Weather20°C (69°F)477 mm (18.8 inches)85%extreme
August Weather20°C (68°F)589 mm (23.2 inches)82%extreme
September Weather20°C (68°F)536 mm (21.1 inches)81%extreme
October Weather20°C (68°F)802 mm (31.6 inches)80%extreme
November Weather20°C (67°F)620 mm (24.4 inches)80%extreme
December Weather19°C (67°F)191 mm (7.5 inches)72%extreme

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