O'Fallon Weather Forecast

    • 66
    • 94

    Chance Rain Showers

    • 64
    • 85

    Chance Thunderstorms

    • 66
    • 87

    Chance Rain Showers

    • 65
    • 82

    Rain Showers Likely

    • 65
    • 82

    Chance Rain Showers

    • 61
    • 81

    Chance Rain Showers

Today 18 Sep St. Charles

Sunny. Highs in the mid 90s. Southeast Winds around 5 Mph.

Tonight 18 Sep St. Charles

Partly cloudy in the Evening, then becoming mostly cloudy. A slight chance of Showers and Thunderstorms. Lows in the mid 60s. Northeast Winds 5 to 10 Mph. Chance of rain 20 percent.

Graph Plots Open in Graphs

  • Temperature Forecast NOAA

  • Temperature Real-Time

O'Fallon Temperature Statistics

September Temperature

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

  • Lowest 8 September, 2025

    41 °F

  • Average September

    70.3 °F

  • Highest 14 September, 2025

    98.1 °F

Climate (2020–Present)

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

Take a look at our website widgetsAvailable free! Find Out More

  • Average Low 2020–2025

    45.8 °F

  • Average 2020–2025

    56.9 °F

  • Average High 2020–2025

    68.1 °F
Get WillyWeather+ to remove ads