Grand Lake St. Marys SPB Weather Forecast

    • 62
    • 82

    Chance Rain Showers

    • 60
    • 78

    Mostly Sunny

    • 63
    • 81

    Mostly Sunny

    • 72
    • 85

    Partly Sunny

    • 69
    • 88

    Chance Rain Showers

    • 61
    • 80

    Partly Sunny

Today 5 Sep Mercer

Partly cloudy. A chance of Showers with a slight chance of Thunderstorms late this Morning, then a slight chance of Showers and Thunderstorms this afternoon. Highs in the lower 80s. Northwest Winds around 5 Mph, becoming north late. Chance of rain 40 percent.

Tonight 5 Sep Mercer

Partly cloudy in the Evening, then becoming mostly clear. Lows around 60. Northeast Winds 5 to 10 Mph.

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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 2 September, 2026

    71.6 °F

  • Average September

    82.6 °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

    43.3 °F

  • Average 2021–2026

    52.5 °F

  • Average High 2021–2026

    61.8 °F
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