Last updated: August 27, 2025
In San Juan, Peru, the average temperature in September hovers around 7°C (46°F), making it a cool but comfortable time of year. Visitors should prepare for varying conditions, with minimums dipping to -5°C (24°F) and maximums reaching up to 19°C (66°F). Expect 93 mm (3.7 in) of precipitation spread across 17 days, contributing to an average humidity of 53%. Whether you're exploring the outdoors or enjoying indoor activities, be ready for a mixture of chilly and mild days!
In September in San Juan, the average temperature is 7°C (46°F), with maximums reaching 19°C (66°F) and minimums dropping as low as -5°C (24°F). Travelers should prepare for a mix of chilly days and milder afternoons, making it essential to pack layers for comfort.
In San Juan in September, the precipitation amount is 93 mm (3.7 in) spread over 17 days.
In San Juan in September, humidity is 53%. With an average temperature of 7°C (46°F), this humidity feels like a crisp chill in the air, making it refreshing but slightly damp, which can be invigorating for travelers exploring the scenery or engaging in outdoor activities.
In San Juan in September, the maximum UV index is 16, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, making it crucial to take protective measures. For detailed information, you can refer to 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 | 8°C (47°F) | 254 mm (10.0 inches) | 89% | extreme |
| February Weather | 8°C (47°F) | 268 mm (10.6 inches) | 90% | extreme |
| March Weather | 8°C (47°F) | 323 mm (12.7 inches) | 90% | extreme |
| April Weather | 7°C (46°F) | 142 mm (5.6 inches) | 90% | extreme |
| May Weather | 6°C (44°F) | 72 mm (2.8 inches) | 84% | extreme |
| June Weather | 6°C (43°F) | 49 mm (1.9 inches) | 67% | extreme |
| July Weather | 6°C (43°F) | 41 mm (1.6 inches) | 53% | extreme |
| August Weather | 6°C (44°F) | 35 mm (1.4 inches) | 47% | extreme |
| September Weather | 7°C (46°F) | 93 mm (3.7 inches) | 53% | extreme |
| October Weather | 8°C (46°F) | 106 mm (4.2 inches) | 67% | extreme |
| November Weather | 8°C (47°F) | 83 mm (3.3 inches) | 75% | extreme |
| December Weather | 8°C (47°F) | 146 mm (5.7 inches) | 82% | extreme |