Flat Lake Weather Forecast

    • 53
    • 72

    Chance Rain Showers

    • 51
    • 58

    Rain Showers Likely

    • 53
    • 61

    Chance Rain Showers

    • 52
    • 69

    Partly Sunny

    • 54
    • 76

    Partly Sunny

    • 49
    • 71

    Mostly Sunny

    • 49
    • 72

    Mostly Sunny

Today 17 Sep McHenry

Mostly cloudy with a slight chance of Showers and Thunderstorms. Highs in the lower 70s. Northeast Winds around 5 Mph. Chance of rain 20 percent.

Tonight 17 Sep McHenry

Cloudy. A slight chance of Showers after midnight. Lows in the lower 50s. Northeast Winds 5 to 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Flat Lake Temperature Statistics

September Temperature

Harvey Municipal Airport (22.4 miles)

  • Lowest 7 September, 2025

    33.8 °F

  • Average September

    59.6 °F

  • Highest 1 September, 2025

    80.6 °F

Climate (2020–Present)

Harvey Municipal Airport (22.4 miles)

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  • Average Low 2020–2025

    30.1 °F

  • Average 2020–2025

    41.2 °F

  • Average High 2020–2025

    51.9 °F
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