Grand Lake St. Marys SPB Weather Forecast

    • 68
    • 80

    Rain Showers Likely

    • 58
    • 78

    Rain Showers

    • 54
    • 66

    Chance Rain Showers

    • 57
    • 67

    Chance Rain Showers

    • 57
    • 67

    Chance Rain Showers

    • 55
    • 68

    Mostly Cloudy

    • 53
    • 71

    Partly Sunny

Today 19 Sep Mercer

Partly cloudy. Highs in the lower 70s.

Tonight 19 Sep Mercer

Mostly cloudy. A chance of Showers and Thunderstorms this Evening, then Showers likely with a slight chance of Thunderstorms after midnight. Lows in the mid 60s. South Winds around 5 Mph. Chance of rain 70 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Grand Lake St. Marys SPB Temperature Statistics

September Temperature

Versailles Darke County Airport (23 miles)

  • Lowest 14 September, 2026

    51.8 °F

  • Average September

    74.2 °F

  • Highest 1 September, 2026

    93.2 °F

Climate (2021–2026)

Versailles Darke County Airport (23 miles)

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  • Average Low 2021–2026

    43.4 °F

  • Average 2021–2026

    52.6 °F

  • Average High 2021–2026

    61.8 °F
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