Flat Lake Weather Forecast

    • 43
    • 69

    Slight Chance Thunderstorms

    • 53
    • 82

    Partly Sunny

    • 59
    • 90

    Mostly Sunny

    • 62
    • 91

    Mostly Sunny

    • 59
    • 86

    Partly Sunny

    • 56
    • 83

    Partly Sunny

Today 23 May McHenry

Mostly sunny with a slight chance of Showers and Thunderstorms. Highs in the upper 60s. West Winds 10 to 15 Mph. Chance of rain 20 percent.

Tonight 23 May McHenry

Mostly clear. Lows in the lower 40s. East Winds around 5 Mph, becoming south after midnight.

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Flat Lake Temperature Statistics

May Temperature

Harvey Municipal Airport (22.4 miles)

  • Lowest 7 May, 2026

    23 °F

  • Average May

    50.9 °F

  • Highest 11 May, 2026

    80.6 °F

Climate (2021–Present)

Harvey Municipal Airport (22.4 miles)

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  • Average Low 2021–2026

    30.3 °F

  • Average 2021–2026

    41.2 °F

  • Average High 2021–2026

    51.9 °F
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