Illiopolis Weather Forecast

    • 69
    • 85

    Becoming Sunny

    • 68
    • 84

    Thunderstorms Likely

    • 54
    • 82

    Rain Showers

    • 46
    • 68

    Mostly Cloudy

    • 52
    • 70

    Mostly Cloudy

    • 57
    • 74

    Mostly Cloudy

    • 60
    • 80

    Slight Chance Thunderstorms

Today 17 May Sangamon

Partly sunny and breezy. Highs in the upper 80s. South Winds 20 to 25 Mph.

Tonight 17 May Sangamon

Mostly clear in the Evening, then becoming partly cloudy. Lows around 70. South Winds 15 to 20 Mph with Gusts up to 30 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Illiopolis Temperature Statistics

May Temperature

Decatur Airport (19.3 miles)

  • Lowest 7 May, 2026

    37.7 °F

  • Average May

    57 °F

  • Highest 12 May, 2026

    80.7 °F

Climate (2021–Present)

Decatur Airport (19.3 miles)

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  • Average Low 2021–2026

    45.4 °F

  • Average 2021–2026

    55.5 °F

  • Average High 2021–2026

    65.6 °F
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