Illiopolis Weather Forecast
- 58
- 90
Mostly Sunny
- 60
- 90
Mostly Sunny
- 64
- 93
Partly Sunny
- 62
- 84
Chance Thunderstorms
- 62
- 84
Chance Rain Showers
- 62
- 81
Chance Rain Showers
Today 16 Sep Sangamon
Sunny. Highs in the lower 90s. Northeast Winds around 5 Mph.
Tonight 16 Sep Sangamon
Mostly clear. Lows in the upper 50s. East Winds around 5 Mph.
Illiopolis Temperature Statistics
September Temperature
Decatur Airport (19.3 miles)
Lowest 8 September, 2025
42.1 °FAverage September
67.9 °FHighest 13 September, 2025
96.1 °F
Climate (2020–Present)
Decatur Airport (19.3 miles)
Average Low 2020–2025
45.2 °FAverage 2020–2025
55.2 °FAverage High 2020–2025
65 °F