Flat Lake Weather Forecast

    • 29
    • 58

    Mostly Sunny

    • 39
    • 59

    Mostly Sunny

    • 47
    • 78

    Slight Chance Thunderstorms

    • 41
    • 71

    Breezy

    • 52
    • 76

    Partly Sunny

    • 50
    • 81

    Breezy

Today 9 May McHenry

Sunny. Highs in the upper 50s. Northwest Winds 10 to 20 Mph.

Tonight 9 May McHenry

Mostly clear. Widespread frost after midnight. Lows in the upper 20s. North Winds 5 to 10 Mph with Gusts up to 25 Mph, becoming northeast 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

    46.8 °F

  • Highest 3 May, 2026

    73.4 °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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