Last updated: June 24, 2025
In San Juan, United States, the average temperature in September is a warm 29°C (84°F), with temperatures ranging from a refreshing 17°C (64°F) to a sizzling 41°C (106°F). During this month, expect approximately 96 mm (3.8 in) of precipitation spread over 11 days, creating a humidity level of around 73%. Whether you're basking in the sun or dodging a shower, September in San Juan offers a unique blend of tropical warmth and refreshing rain.
In September in San Juan, the average temperature is 29°C (84°F), with maximums reaching up to 41°C (106°F) and minimums dipping as low as 17°C (64°F). This climate offers a warm and varied experience, making it ideal for travelers seeking both sunshine and cooler moments.
In San Juan in September, the precipitation amount is 96 mm (3.8 in) spread over 11 days, resulting in a significant accumulation of rainfall.
In San Juan in September, humidity is 73%. With an average temperature of 29°C (84°F), this humidity feels like a warm blanket wrapped around you, making travel slightly uncomfortable as you sweat and seek shade, yet still inviting you to explore the vibrant local culture and activities.
In San Juan in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the 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 September’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 (62°F) | 20 mm (0.8 inches) | 83% | high |
| February Weather | 18°C (65°F) | 21 mm (0.8 inches) | 79% | very high |
| March Weather | 22°C (72°F) | 31 mm (1.2 inches) | 76% | very high |
| April Weather | 25°C (78°F) | 31 mm (1.2 inches) | 77% | extreme |
| May Weather | 28°C (83°F) | 87 mm (3.4 inches) | 80% | extreme |
| June Weather | 30°C (86°F) | 81 mm (3.2 inches) | 73% | extreme |
| July Weather | 30°C (87°F) | 100 mm (3.9 inches) | 66% | extreme |
| August Weather | 31°C (88°F) | 22 mm (0.9 inches) | 65% | extreme |
| September Weather | 29°C (84°F) | 96 mm (3.8 inches) | 73% | extreme |
| October Weather | 25°C (77°F) | 51 mm (2.0 inches) | 76% | very high |
| November Weather | 20°C (69°F) | 30 mm (1.2 inches) | 80% | high |
| December Weather | 18°C (64°F) | 21 mm (0.8 inches) | 86% | high |