Climate almanac
O'Fallon
Missouri, United States · 38.81°, -90.70°
What is the weather like in O'Fallon in September?
In September, O'Fallon is typically 82°F (28°C) during the day and 61°F (16°C) at night. The month brings about 2.7 in (69 mm) of precipitation in total.
- Average high82°F (28°C)
- Average low61°F (16°C)
- Precipitation2.7 in (69 mm)
- Clear or mostly clear days15
- Based on2016-2025 daily ERA5 reanalysis data (10-year normals)