Grand Lake Saint Marys State Park Weather Forecast

    • 41
    • 57

    Chance Rain Showers

    • 41
    • 59

    Slight Chance Rain Showers

    • 44
    • 63

    Partly Sunny

    • 49
    • 65

    Mostly Cloudy

    • 53
    • 64

    Chance Rain Showers

    • 52
    • 67

    Chance Rain Showers

Today 22 May Mercer

Cloudy with a 50 percent chance of Showers. Unseasonably cold with Highs in the upper 50s. West Winds around 15 Mph with Gusts up to 25 Mph.

Tonight 22 May Mercer

Partly cloudy with a slight chance of Showers in the Evening, then mostly clear after midnight. Lows around 40. Northwest Winds 10 to 15 Mph with Gusts up to 25 Mph. Chance of rain 20 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Grand Lake Saint Marys State Park Temperature Statistics

May Temperature

Versailles Darke County Airport (22.4 miles)

  • Lowest 19 May, 2025

    44.6 °F

  • Average May

    64.4 °F

  • Highest 15 May, 2025

    84.2 °F

Climate (2020–Present)

Versailles Darke County Airport (22.4 miles)

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  • Average Low 2020–2025

    43.3 °F

  • Average 2020–2025

    52.4 °F

  • Average High 2020–2025

    61.7 °F
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