Grand Lake Saint Marys State Park Weather Forecast

    • 56
    • 71

    Increasing Clouds

    • 56
    • 82

    Rain Showers

    • 42
    • 64

    Rain Showers

    • 48
    • 62

    Chance Rain Showers

    • 41
    • 58

    Slight Chance Rain Showers

    • 41
    • 58

    Partly Sunny

Today 17 Oct Mercer

Partly cloudy. Highs in the lower 70s. South Winds 5 to 10 Mph.

Tonight 17 Oct Mercer

Mostly cloudy. Lows in the mid 50s. South Winds around 10 Mph with Gusts up to 20 Mph.

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Grand Lake Saint Marys State Park Temperature Statistics

October Temperature

Versailles Darke County Airport (22.4 miles)

  • Lowest 10 October, 2025

    37.4 °F

  • Average October

    61.6 °F

  • Highest 3 October, 2025

    86 °F

Climate (2020–Present)

Versailles Darke County Airport (22.4 miles)

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  • Average Low 2020–2025

    43.4 °F

  • Average 2020–2025

    52.4 °F

  • Average High 2020–2025

    61.5 °F
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