O'Fallon Weather Forecast

    • 71
    • 89

    Decreasing Clouds

    • 72
    • 90

    Mostly Sunny

    • 76
    • 93

    Mostly Sunny

    • 76
    • 93

    Mostly Sunny

    • 74
    • 92

    Partly Sunny

    • 72
    • 88

    Chance Thunderstorms

Today 7 Aug St. Charles

Mostly sunny. A chance of Showers and Thunderstorms in the afternoon. Warmer with Highs in the upper 80s. Southwest Winds around 5 Mph. Chance of rain 30 percent. Heat index Values up to 100 in the afternoon.

Tonight 7 Aug St. Charles

Mostly cloudy with a chance of Showers and Thunderstorms. Near steady temperature in the upper 60s. South Winds around 5 Mph. Chance of rain 50 percent.

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  • Temperature Real-Time

O'Fallon Temperature Statistics

August Temperature

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

  • Lowest 3 August, 2026

    63 °F

  • Average August

    74.5 °F

  • Highest 4 August, 2026

    89.1 °F

Climate (2021–2026)

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

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  • Average Low 2021–2026

    46.1 °F

  • Average 2021–2026

    57.5 °F

  • Average High 2021–2026

    68.9 °F
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