Saint Charles Weather Forecast

    • 75
    • 98

    Slight Chance Thunderstorms

    • 76
    • 97

    Hot

    • 75
    • 97

    Hot

    • 70
    • 93

    Rain Showers Likely

    • 63
    • 83

    Chance Thunderstorms

    • 59
    • 76

    Mostly Cloudy

    • 61
    • 78

    Partly Sunny

Today 17 Sep St. Charles

Sunny with a chance of Showers and Thunderstorms. Hot. Near steady temperature in the mid 90s. West Winds around 5 Mph. Chance of rain 30 percent. Heat index Values up to 106.

Tonight 17 Sep St. Charles

Mostly clear. A slight chance of Showers and Thunderstorms this evening. Lows in the lower 70s. Southwest Winds around 5 Mph, becoming northwest after midnight. Chance of rain 20 percent. Heat index Values up to 101 early this evening.

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Saint Charles Temperature Statistics

September Temperature

St. Louis Lambert International Airport (6.2 miles)

  • Lowest 14 September, 2026

    63 °F

  • Average September

    83.3 °F

  • Highest 5 September, 2026

    101.6 °F

Climate (2021–2026)

St. Louis Lambert International Airport (6.2 miles)

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  • Average Low 2021–2026

    50.7 °F

  • Average 2021–2026

    60.2 °F

  • Average High 2021–2026

    69.8 °F
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