Illiopolis Weather Forecast

    • 75
    • 94

    Becoming Sunny

    • 77
    • 97

    Hot

    • 77
    • 97

    Hot

    • 74
    • 94

    Chance Thunderstorms

    • 70
    • 92

    Slight Chance Thunderstorms

    • 67
    • 90

    Mostly Sunny

Today 31 Aug Sangamon

Sunny, hot with Highs in the mid 90s. South Winds 5 to 10 Mph. Heat index Values up to 101 in the afternoon.

Tonight 31 Aug Sangamon

Mostly clear. Lows around 70. South Winds around 10 Mph with Gusts up to 20 Mph.

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Illiopolis Temperature Statistics

August Temperature

Decatur Airport (19.3 miles)

  • Lowest 25 August, 2026

    54.6 °F

  • Average August

    75.2 °F

  • Highest 11 August, 2026

    92.6 °F

Climate (2021–2026)

Decatur Airport (19.3 miles)

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  • Average Low 2021–2026

    45.3 °F

  • Average 2021–2026

    55.5 °F

  • Average High 2021–2026

    65.6 °F
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