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January Weather in San Juan, United States

Last updated: June 24, 2025

In San Juan, United States, the average temperature in January hovers around 16°C (62°F), offering a comfortably mild experience. However, be prepared for temperature fluctuations, as it can dip to a brisk -1°C (31°F) or soar to a warm 34°C (94°F). Rainfall is moderate, with 20 mm (0.8 in) of precipitation expected over about 4 days. Visitors can anticipate a high average humidity of 83%, adding a touch of tropical warmth to the atmosphere.

January Temperature in San Juan

In January in San Juan, the average temperature is 16°C (62°F). Maximum temperatures can reach up to 34°C (94°F), while minimums can drop as low as -1°C (31°F). This variability in weather conditions makes San Juan an ideal destination for travelers seeking a diverse climate experience.

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

The chart illustrates January 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, January typically has an average temperature of 16°C (62°F), with highs reaching up to 34°C (94°F) and lows dropping to around -1°C (31°F).
JanFebMarAprMayJunJulAugSepOctNovDec616572778285868884776964
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.

January Precipitation in San Juan

In San Juan in January, the total precipitation amount is 20 mm (0.8 in) spread over a period of 4 days.

January Precipitation Trends in San Juan

The chart displays monthly precipitation patterns in San Juan, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In San Juan, January typically receives around 20 mm (0.8 inches) of precipitation spread over approximately 4 days.
JanFebMarAprMayJunJulAugSepOctNovDec2021313187811002296513021
Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.
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January Humidity in San Juan

In San Juan in January humidity is 83%. With an average temperature of 16°C (62°F), this humidity feels like a warm, sticky embrace that can make traveling feel a bit heavy, leaving you longing for refreshing breezes and shaded spots to relax in.

January Average Humidity in San Juan

This chart illustrates the average monthly humidity levels in San Juan, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in San Juan is approximately 83%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec83%79%76%77%80%73%66%65%73%76%80%86%
Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in San Juan

In San Juan in January, the maximum UV index is 6, which corresponds to a high Exposure Category. The time to burn is approximately 25 minutes. To find the hourly UV index in San Juan, you can refer to this Hourly UV Index in San Juan.

Maximum UV Index Levels in San Juan for January

The chart shows the monthly maximum UV Index (UVI) for San Juan in January, 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 January, the maximum UV index in San Juan typically reaches 6, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec6910111212121211976
Data source: San Juan January 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 January 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 January’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 January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather16°C (62°F)20 mm (0.8 inches)83%high
February Weather18°C (65°F)21 mm (0.8 inches)79%very high
March Weather22°C (72°F)31 mm (1.2 inches)76%very high
April Weather25°C (78°F)31 mm (1.2 inches)77%extreme
May Weather28°C (83°F)87 mm (3.4 inches)80%extreme
June Weather30°C (86°F)81 mm (3.2 inches)73%extreme
July Weather30°C (87°F)100 mm (3.9 inches)66%extreme
August Weather31°C (88°F)22 mm (0.9 inches)65%extreme
September Weather29°C (84°F)96 mm (3.8 inches)73%extreme
October Weather25°C (77°F)51 mm (2.0 inches)76%very high
November Weather20°C (69°F)30 mm (1.2 inches)80%high
December Weather18°C (64°F)21 mm (0.8 inches)86%high

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