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December Weather in San Marcos, Costa Rica

Last updated: August 23, 2025

In December, the average temperature in San Marcos, Costa Rica is a pleasant 17°C (64°F), with temperatures ranging from a minimum of 12°C (54°F) to a maximum of 24°C (75°F). Expect around 78 mm (3.1 in) of precipitation over approximately 11 days, complemented by an average humidity of 72%.

December Temperature in San Marcos

In December in San Marcos, the average temperature is 17°C (64°F). The maximum can reach 24°C (75°F), while the minimum can drop to as low as 12°C (54°F). This mild climate makes it an ideal time for travelers to explore and enjoy outdoor activities.

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

The chart illustrates December 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, December typically has an average temperature of 17°C (64°F), with highs reaching up to 24°C (75°F) and lows dropping to around 12°C (54°F).
JanFebMarAprMayJunJulAugSepOctNovDec636464656565656564646463
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.

December Precipitation in San Marcos

In San Marcos in December, the precipitation amount is 78 mm (3.1 in) over the course of 11 days.

December Precipitation Trends in San Marcos

The chart displays monthly precipitation patterns in San Marcos, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In San Marcos, December typically receives around 78 mm (3.1 inches) of precipitation spread over approximately 11 days.
JanFebMarAprMayJunJulAugSepOctNovDec35192815553239931540350860127278
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in San Marcos

In San Marcos in December humidity is 72%. With an average temperature of 17°C (64°F), this humidity feels like a warm, sticky embrace, making travel comfortable yet slightly muggy, especially during midday when the warmth is more pronounced.

December Average Humidity in San Marcos

This chart illustrates the average monthly humidity levels in San Marcos, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in San Marcos is approximately 72%, 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 December generated using information from the Copernicus Climate Change Service.

December UV Index in San Marcos

In San Marcos in December, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in San Marcos.

Maximum UV Index Levels in San Marcos for December

The chart shows the monthly maximum UV Index (UVI) for San Marcos in December, 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 December, the maximum UV index in San Marcos typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec121415161514151414141211
Data source: San Marcos December 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 December 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 December’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 December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather17°C (63°F)35 mm (1.4 inches)68%extreme
February Weather18°C (64°F)19 mm (0.8 inches)68%extreme
March Weather18°C (65°F)28 mm (1.1 inches)66%extreme
April Weather18°C (65°F)155 mm (6.1 inches)67%extreme
May Weather18°C (65°F)532 mm (21.0 inches)69%extreme
June Weather18°C (66°F)399 mm (15.7 inches)84%extreme
July Weather18°C (65°F)315 mm (12.4 inches)85%extreme
August Weather18°C (65°F)403 mm (15.9 inches)82%extreme
September Weather18°C (65°F)508 mm (20.0 inches)81%extreme
October Weather18°C (64°F)601 mm (23.7 inches)80%extreme
November Weather18°C (64°F)272 mm (10.7 inches)80%extreme
December Weather17°C (64°F)78 mm (3.1 inches)72%extreme

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