December in San Juan averages a daily high of 29.1°C with nights around 21.8°C. Expect roughly 18.9 wet days totalling 158.3mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit San Juan is November–April.
Based on TOA BAJA LEVITTOWN, PR US (7.4km), 1995–2024. 12 years of December data.