San Juan weather in January

Averages from 2021–2025 (155 days of record).

Average high

82°F

Average low

72°F

Rainy days

~14 per month

Total precipitation

2.2 in

Warmest recorded

90°F

Coldest recorded

67°F

Expect January days in San Juan to top out around 82°F and cool to about 72°F overnight, with roughly 14 days of measurable rain across the month. In recent years January has ranged from 67°F to 90°F.