Alton Weather Forecast

    • 70
    • 88

    Thunderstorms

    • 68
    • 84

    Thunderstorms

    • 66
    • 84

    Partly Sunny

    • 67
    • 86

    Mostly Sunny

    • 66
    • 87

    Mostly Sunny

    • 66
    • 85

    Partly Sunny

Today 18 Aug Madison

Sunny. Highs in the upper 80s. Southwest Winds around 5 Mph.

Tonight 18 Aug Madison

Mostly clear in the Evening, then mostly cloudy with numerous Showers and Thunderstorms after midnight. Lows around 70. South Winds around 5 Mph. Chance of rain 70 percent.

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Alton Temperature Statistics

August Temperature

St. Louis Regional Airport (8.1 miles)

  • Lowest 3 August, 2026

    63.5 °F

  • Average August

    76.7 °F

  • Highest 11 August, 2026

    95 °F

Climate (2021–2026)

St. Louis Regional Airport (8.1 miles)

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  • Average Low 2021–2026

    46.6 °F

  • Average 2021–2026

    54.5 °F

  • Average High 2021–2026

    66.7 °F
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