Climate almanac
Monmouth
Illinois, United States · 40.91°, -90.65°
What is the weather like in Monmouth in September?
In September, Monmouth is typically 80°F (27°C) during the day and 59°F (15°C) at night. The month brings about 2.9 in (74 mm) of precipitation in total.
- Average high80°F (27°C)
- Average low59°F (15°C)
- Precipitation2.9 in (74 mm)
- Clear or mostly clear days15
- Based on2016-2025 daily ERA5 reanalysis data (10-year normals)