Illiopolis Weather Forecast

    • 61
    • 85

    Slight Chance Thunderstorms

    • 58
    • 82

    Slight Chance Thunderstorms

    • 55
    • 81

    Sunny

    • 57
    • 81

    Mostly Sunny

    • 63
    • 85

    Partly Sunny

    • 65
    • 86

    Chance Rain Showers

    • 66
    • 86

    Chance Thunderstorms

Today 31 May Sangamon

Mostly cloudy. Near steady temperature around 80. Southeast Winds 5 to 10 Mph.

Tonight 31 May Sangamon

Mostly cloudy. A slight chance of Showers and Thunderstorms after midnight. Lows in the lower 60s. Southeast Winds around 5 Mph. Chance of rain 20 percent.

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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

    62.5 °F

  • Highest 28 May, 2026

    86.6 °F

Climate (2021–Present)

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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