O'Fallon Weather Forecast

    • 46
    • 64

    Increasing Clouds

    • 49
    • 65

    Rain Showers

    • 38
    • 54

    Chance Rain

    • 24
    • 44

    Partly Sunny

    • 24
    • 35

    Mostly Sunny

    • 32
    • 48

    Partly Sunny

    • 35
    • 51

    Mostly Cloudy

Today 7 Jan St. Charles

Mostly sunny. Highs in the lower 60s. South Winds 5 to 10 Mph.

Tonight 7 Jan St. Charles

Partly cloudy in the Evening, then becoming mostly cloudy. Not as cool with Lows in the mid 40s. Southeast Winds 5 to 10 Mph with Gusts up to 20 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

O'Fallon Temperature Statistics

January Temperature

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

  • Lowest 4 January, 2026

    19 °F

  • Average January

    35 °F

  • Highest 5 January, 2026

    62.1 °F

Climate (2021–Present)

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

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  • Average Low 2021–2026

    46 °F

  • Average 2021–2026

    57.1 °F

  • Average High 2021–2026

    68.3 °F
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