Illiopolis Weather Forecast

    • 57
    • 81

    Mostly Sunny

    • 63
    • 84

    Partly Sunny

    • 64
    • 87

    Chance Thunderstorms

    • 62
    • 85

    Mostly Sunny

    • 64
    • 85

    Partly Sunny

    • 68
    • 86

    Mostly Cloudy

Today 24 Aug Sangamon

Patchy fog in the morning. Mostly sunny. Highs in the lower 80s. Light and variable Winds, becoming north around 5 Mph in the afternoon.

Tonight 24 Aug Sangamon

Mostly clear. Patchy fog. Lows in the mid 50s. Light and variable Winds.

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Illiopolis Temperature Statistics

August Temperature

Decatur Airport (19.3 miles)

  • Lowest 21 August, 2026

    57.9 °F

  • Average August

    76.4 °F

  • Highest 11 August, 2026

    92.6 °F

Climate (2021–2026)

Decatur Airport (19.3 miles)

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  • Average Low 2021–2026

    45.4 °F

  • Average 2021–2026

    55.5 °F

  • Average High 2021–2026

    65.6 °F
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