Grand Lake St. Marys SPB Weather Forecast

    • 18
    • 51

    Rain Showers

    • 23
    • 25

    Slight Chance Snow Showers

    • 23
    • 43

    Mostly Cloudy

    • 19
    • 30

    Partly Sunny

    • 32
    • 36

    Slight Chance Rain

    • 35
    • 45

    Mostly Cloudy

Today 18 Dec Mercer

Partly cloudy with a chance of Showers in the Morning, then Showers in the afternoon. Breezy with Highs in the lower 50s. South Winds 15 to 25 Mph with Gusts up to 45 Mph. Chance of rain 100 percent.

Tonight 18 Dec Mercer

Rain Showers in the Evening, then a chance of snow and rain Showers after midnight. Little or no snow accumulation. Breezy, cooler with Lows 15 to 20. West Winds 15 to 25 Mph with Gusts up to 35 Mph. Chance of precipitation 100 percent.

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Grand Lake St. Marys SPB Temperature Statistics

December Temperature

Versailles Darke County Airport (23 miles)

  • Lowest 14 December, 2025

    -4 °F

  • Average December

    22.9 °F

  • Highest 10 December, 2025

    41 °F

Climate (2020–Present)

Versailles Darke County Airport (23 miles)

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  • Average Low 2020–2025

    43.2 °F

  • Average 2020–2025

    52.3 °F

  • Average High 2020–2025

    61.4 °F
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