Climate almanac
Monticello
Illinois, United States · 40.03°, -88.57°
What is the weather like in Monticello in September?
In September, Monticello is typically 81°F (27°C) during the day and 60°F (15°C) at night. The month brings about 3.0 in (77 mm) of precipitation in total.
- Average high81°F (27°C)
- Average low60°F (15°C)
- Precipitation3.0 in (77 mm)
- Clear or mostly clear days15
- Based on2016-2025 daily ERA5 reanalysis data (10-year normals)