Last updated: August 27, 2025
In December, the average temperature in San Juan, Mexico hovers around 17°C (64°F), making it a mild and inviting destination. However, temperatures can fluctuate, with minimums dipping to 2°C (35°F) and maximums soaring to 36°C (97°F). Visitors can expect some rainfall, with precipitation averaging 20 mm (0.8 in) over approximately 3 days. Notably, the average humidity stands at 86%, contributing to the region's lush atmosphere.
In December in San Juan, the average temperature is 17°C (64°F). Maximum temperatures can reach 36°C (97°F), while minimums can drop as low as 2°C (35°F). Be prepared for a wide range of temperatures during your travels!
In San Juan in December, the precipitation amount is 20 mm (0.8 in) accumulated over a period of 3 days.
In San Juan in December humidity is 86%. With an average temperature of 17°C (64°F), this humidity feels like a warm blanket enveloping you, making travel quite uncomfortable as the moisture clings to your skin and the air feels thick, damp, and heavy.
In San Juan in December, 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.
UV Risk Categories
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.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 16°C (61°F) | 20 mm (0.8 inches) | 84% | high |
| February Weather | 18°C (65°F) | 13 mm (0.5 inches) | 83% | very high |
| March Weather | 23°C (73°F) | 25 mm (1.0 inches) | 78% | very high |
| April Weather | 25°C (78°F) | 46 mm (1.8 inches) | 81% | extreme |
| May Weather | 28°C (83°F) | 86 mm (3.4 inches) | 82% | extreme |
| June Weather | 30°C (86°F) | 86 mm (3.4 inches) | 74% | extreme |
| July Weather | 31°C (87°F) | 78 mm (3.1 inches) | 68% | extreme |
| August Weather | 31°C (89°F) | 16 mm (0.6 inches) | 67% | extreme |
| September Weather | 28°C (83°F) | 119 mm (4.7 inches) | 75% | extreme |
| October Weather | 24°C (76°F) | 56 mm (2.2 inches) | 78% | very high |
| November Weather | 20°C (68°F) | 23 mm (0.9 inches) | 83% | high |
| December Weather | 17°C (64°F) | 20 mm (0.8 inches) | 86% | high |