Last updated: June 24, 2025
In September, the average temperature in Saint Louis, United States hovers around 18°C (64°F). Expect a range that can dip to a chilly 1°C (34°F) and soar up to a warm 35°C (95°F). With 98 mm (3.9 in) of precipitation spread over 10 days, be prepared for some rainy spells. Humidity levels linger around a cozy 80%, adding to the area's distinctive climate.
In September in Saint Louis, the average temperature is 18°C (64°F). The maximum can reach 35°C (95°F), while the minimum can drop as low as 1°C (34°F). This range makes Saint Louis an ideal destination for travelers seeking a diverse climate, offering both warm days and cool nights.
In Saint Louis in September, the total precipitation amount is 98 mm (3.9 in) recorded over a span of 10 days.
In Saint Louis in September humidity is 80%. With an average temperature of 18°C (64°F), this humidity feels like a warm, damp blanket wrapping around you, making travel a bit more exhausting as the air thickens and the heat clings to your skin.
In Saint Louis in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Saint Louis.
UV Risk Categories
Weather in Saint Louis varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Saint Louis, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -4°C (24°F) | 55 mm (2.2 inches) | 88% | low |
| February Weather | -4°C (25°F) | 59 mm (2.3 inches) | 87% | moderate |
| March Weather | 2°C (35°F) | 58 mm (2.3 inches) | 85% | moderate |
| April Weather | 7°C (46°F) | 86 mm (3.4 inches) | 86% | very high |
| May Weather | 15°C (59°F) | 115 mm (4.5 inches) | 80% | very high |
| June Weather | 20°C (69°F) | 113 mm (4.5 inches) | 80% | very high |
| July Weather | 23°C (74°F) | 67 mm (2.7 inches) | 80% | very high |
| August Weather | 22°C (71°F) | 81 mm (3.2 inches) | 80% | very high |
| September Weather | 18°C (64°F) | 98 mm (3.9 inches) | 80% | high |
| October Weather | 11°C (52°F) | 120 mm (4.7 inches) | 84% | moderate |
| November Weather | 3°C (38°F) | 57 mm (2.2 inches) | 89% | moderate |
| December Weather | -1°C (31°F) | 63 mm (2.5 inches) | 86% | low |