O'Fallon Weather Forecast

    • 70
    • 85

    Chance Thunderstorms

    • 74
    • 87

    Chance Thunderstorms

    • 76
    • 93

    Slight Chance Thunderstorms

    • 75
    • 94

    Chance Thunderstorms

    • 77
    • 95

    Slight Chance Thunderstorms

    • 77
    • 97

    Hot

Today 17 Jul St. Charles

Partly sunny. A slight chance of Showers and Thunderstorms in the Morning, then a chance of Showers and Thunderstorms in the afternoon. Humid with Highs in the upper 80s. North Winds around 5 Mph. Chance of rain 50 percent. Heat index Values up to 100.

Tonight 17 Jul St. Charles

Mostly cloudy with a chance of Showers and Thunderstorms. Lows in the lower 70s. Northeast Winds around 5 Mph. Chance of rain 50 percent.

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O'Fallon Temperature Statistics

July Temperature

St. Louis, Spirit Of St. Louis Airport (10.6 miles)

  • Lowest 2 July, 2025

    62.1 °F

  • Average July

    79.5 °F

  • Highest 4 July, 2025

    93.7 °F

Climate (2020–Present)

St. Louis, Spirit Of St. Louis Airport (10.6 miles)

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  • Average Low 2020–2025

    45.8 °F

  • Average 2020–2025

    56.8 °F

  • Average High 2020–2025

    68 °F
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