San Juan weather in May

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

Average high: 87°F
Average low: 75°F
Rainy days: ~19 per month
Total precipitation: 3.4 in
Warmest recorded: 94°F
Coldest recorded: 71°F

Expect May days in San Juan to top out around 87°F and cool to about 75°F overnight, with roughly 19 days of measurable rain across the month. In recent years May has ranged from 71°F to 94°F.

Other months

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Current San Juan forecast → · Historical data by Open-Meteo (ERA5).