O'Fallon Weather Forecast

    • 74
    • 95

    Becoming Sunny

    • 76
    • 97

    Hot

    • 77
    • 96

    Sunny

    • 77
    • 96

    Slight Chance Thunderstorms

    • 76
    • 94

    Chance Thunderstorms

    • 75
    • 94

    Chance Rain Showers

    • 74
    • 92

    Chance Thunderstorms

Today 29 Jun St. Clair

Mostly sunny. Hot. Near steady temperature in the lower 90s. South Winds 10 to 15 Mph. Heat index Values up to 110.

Tonight 29 Jun St. Clair

Partly cloudy this Evening, then clearing. Lows in the mid 70s. South Winds 10 to 15 Mph. Heat index Values up to 108 early this evening.

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O'Fallon Temperature Statistics

June Temperature

Belleville, Scott AFB/MidAmerica Airport (4.3 miles)

  • Lowest 3 June, 2026

    55.2 °F

  • Average June

    75.4 °F

  • Highest 9 June, 2026

    92.8 °F

Climate (2021–2026)

Belleville, Scott AFB/MidAmerica Airport (4.3 miles)

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  • Average Low 2021–2026

    47.8 °F

  • Average 2021–2026

    57.8 °F

  • Average High 2021–2026

    68 °F
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