Illiopolis Weather Forecast

    • 50
    • 77

    Sunny

    • 62
    • 82

    Mostly Sunny

    • 68
    • 85

    Mostly Cloudy

    • 61
    • 80

    Rain Showers Likely

    • 56
    • 70

    Chance Rain Showers

    • 57
    • 71

    Slight Chance Rain Showers

Today 28 Sep Sangamon

Sunny. Highs in the upper 70s. Northeast Winds around 5 Mph.

Tonight 28 Sep Sangamon

Clear. Lows around 50. East Winds around 5 Mph.

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Illiopolis Temperature Statistics

September Temperature

Decatur Airport (19.3 miles)

  • Lowest 14 September, 2026

    54.6 °F

  • Average September

    75.7 °F

  • Highest 15 September, 2026

    99.6 °F

Climate (2021–2026)

Decatur Airport (19.3 miles)

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  • Average Low 2021–2026

    45.4 °F

  • Average 2021–2026

    55.6 °F

  • Average High 2021–2026

    65.6 °F
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