Last updated: August 27, 2025
In September, the average temperature in San Juan, Mexico hovers around 28°C (84°F). Expect a cozy minimum of 24°C (76°F), while the mercury can rise to a maximum of 36°C (97°F). However, be prepared for a wet spell, as 184 mm (7.2 in) of precipitation is expected over 22 days, accompanied by an average humidity of 79%.
In September in San Juan, the average temperature is 28°C (84°F), with maximums reaching 36°C (97°F) and minimums dropping as low as 24°C (76°F). This warm climate makes San Juan an ideal destination for travelers seeking sunshine and outdoor activities.
In San Juan in September, the total precipitation amount reaches 184 mm (7.2 in) over the course of 22 days.
In San Juan in September, humidity is 79%. With an average temperature of 28°C (84°F), this humidity feels like a warm blanket enveloping you, making travel feel a bit like stepping into a sauna—it's sticky and can be quite exhausting, so staying hydrated and taking breaks in the shade is essential.
In San Juan in September, the maximum UV index is 12, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, underscoring the importance of sun protection. For detailed information, 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 | 24°C (76°F) | 68 mm (2.7 inches) | 81% | very high |
| February Weather | 26°C (78°F) | 24 mm (0.9 inches) | 80% | extreme |
| March Weather | 27°C (81°F) | 20 mm (0.8 inches) | 76% | extreme |
| April Weather | 29°C (84°F) | 31 mm (1.2 inches) | 74% | extreme |
| May Weather | 30°C (87°F) | 45 mm (1.8 inches) | 74% | extreme |
| June Weather | 29°C (84°F) | 252 mm (9.9 inches) | 74% | extreme |
| July Weather | 30°C (85°F) | 54 mm (2.1 inches) | 79% | extreme |
| August Weather | 29°C (85°F) | 108 mm (4.2 inches) | 80% | extreme |
| September Weather | 28°C (84°F) | 184 mm (7.2 inches) | 79% | extreme |
| October Weather | 28°C (82°F) | 235 mm (9.3 inches) | 81% | extreme |
| November Weather | 26°C (79°F) | 138 mm (5.5 inches) | 84% | very high |
| December Weather | 25°C (77°F) | 54 mm (2.1 inches) | 85% | very high |