Steffan Reservoir Weather Forecast

    • 56
    • 73

    Slight Chance Thunderstorms

    • 56
    • 70

    Chance Rain Showers

    • 59
    • 76

    Chance Thunderstorms

    • 60
    • 80

    Partly Sunny

    • 55
    • 77

    Chance Thunderstorms

    • 54
    • 72

    Slight Chance Thunderstorms

Today 18 Sep Knox

Partly sunny this Morning, then mostly cloudy with a slight chance of Showers and Thunderstorms this afternoon. Highs in the lower 70s. Southwest Winds 10 to 15 Mph. Chance of rain 20 percent.

Tonight 18 Sep Knox

A slight chance of Thunderstorms in the evening. Mostly cloudy with a slight chance of Showers. Lows in the mid 50s. West Winds 5 to 10 Mph. Chance of rain 20 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Steffan Reservoir Temperature Statistics

September Temperature

Yankton, Chan Gurney Municipal Airport (11.2 miles)

  • Lowest 7 September, 2025

    41 °F

  • Average September

    66.9 °F

  • Highest 16 September, 2025

    89.1 °F

Climate (2020–Present)

Yankton, Chan Gurney Municipal Airport (11.2 miles)

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  • Average Low 2020–2025

    39.1 °F

  • Average 2020–2025

    50 °F

  • Average High 2020–2025

    61.3 °F
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