Flat Lake Weather Forecast

    • 58
    • 72

    Rain Showers

    • 55
    • 63

    Rain Showers Likely

    • 54
    • 66

    Partly Sunny

    • 55
    • 72

    Partly Sunny

    • 54
    • 73

    Partly Sunny

    • 53
    • 70

    Mostly Sunny

    • 53
    • 70

    Mostly Sunny

Today 18 Sep Marshall

Cloudy with a 50 percent chance of Thunderstorms. Near steady temperature around 70. East Winds 5 to 10 Mph with Gusts up to 20 Mph.

Tonight 18 Sep Marshall

Mostly cloudy. A slight chance of Thunderstorms late this Evening, then a chance of Thunderstorms. Patchy fog. Lows in the upper 50s. East Winds 5 to 10 Mph. Chance of rain 40 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Flat Lake Temperature Statistics

September Temperature

Sisseton, Sisseton Municipal Airport (21.7 miles)

  • Lowest 7 September, 2025

    33.1 °F

  • Average September

    62.4 °F

  • Highest 14 September, 2025

    86 °F

Climate (2020–Present)

Sisseton, Sisseton Municipal Airport (21.7 miles)

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  • Average Low 2020–2025

    36.1 °F

  • Average 2020–2025

    46.7 °F

  • Average High 2020–2025

    57.1 °F
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