San Juan weather in August

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

Average high: 87°F
Average low: 78°F
Rainy days: ~20 per month
Total precipitation: 4.1 in
Warmest recorded: 92°F
Coldest recorded: 73°F

Expect August days in San Juan to top out around 87°F and cool to about 78°F overnight, with roughly 20 days of measurable rain across the month. In recent years August has ranged from 73°F to 92°F.

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