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December Weather in San Juan, Mexico

Last updated: August 27, 2025

In San Juan, Mexico, the average temperature in December is a pleasant 21°C (70°F). Expect temperatures to range from a cool 9°C (48°F) to a warm 31°C (88°F). With an average humidity of 76%, the atmosphere can feel quite muggy. Fortunately, you can look forward to minimal precipitation, with just 2 mm (0.1 in) of rain expected during 0 days of the month. Enjoy the mild weather!

December Temperature in San Juan

In December in San Juan, the average temperature is 21°C (70°F), with maximums reaching 31°C (88°F) and minimums dropping as low as 9°C (48°F). This makes it a pleasant time for outdoor activities and exploration.

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

The chart illustrates December temperature patterns in San Juan, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Juan, December typically has an average temperature of 21°C (70°F), with highs reaching up to 31°C (88°F) and lows dropping to around 9°C (48°F).
JanFebMarAprMayJunJulAugSepOctNovDec717378808177777675757270
Data source: Temperature data for San Juan 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 Juan

In San Juan in December, the precipitation amount is 2 mm (0.1 in) during a span of 0 days.

December Precipitation Trends in San Juan

The chart displays monthly precipitation patterns in San Juan, 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 Juan, December typically receives around 2 mm (0.1 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec232060318344445396231432
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in San Juan

In San Juan in December, humidity is 76%. With an average temperature of 21°C (70°F), this humidity feels like a warm, muggy embrace that can make outdoor activities feel more strenuous, prompting travelers to take frequent breaks and seek shade to stay comfortable during their adventures.

December Average Humidity in San Juan

This chart illustrates the average monthly humidity levels in San Juan, 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 Juan is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec70%65%59%60%67%80%81%83%83%80%77%76%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in San Juan

In San Juan in December, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in San Juan.

Maximum UV Index Levels in San Juan for December

The chart shows the monthly maximum UV Index (UVI) for San Juan 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 Juan typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec911131313141313131198
Data source: San Juan 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 Juan Compares to Other Months

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

This table compares monthly weather conditions in San Juan, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather22°C (71°F)2 mm (0.1 inches)70%very high
February Weather23°C (74°F)3 mm (0.1 inches)65%extreme
March Weather25°C (78°F)2 mm (0.1 inches)59%extreme
April Weather27°C (80°F)0 mm (0.0 inches)60%extreme
May Weather27°C (81°F)60 mm (2.4 inches)67%extreme
June Weather25°C (78°F)318 mm (12.5 inches)80%extreme
July Weather25°C (77°F)344 mm (13.5 inches)81%extreme
August Weather24°C (76°F)445 mm (17.5 inches)83%extreme
September Weather24°C (75°F)396 mm (15.6 inches)83%extreme
October Weather24°C (75°F)231 mm (9.1 inches)80%extreme
November Weather22°C (73°F)43 mm (1.7 inches)77%very high
December Weather21°C (70°F)2 mm (0.1 inches)76%very high

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