Lake Koshkonong Weather Forecast

    • 70
    • 89

    Chance Thunderstorms

    • 63
    • 84

    Partly Sunny

    • 61
    • 81

    Partly Sunny

    • 63
    • 81

    Mostly Cloudy

    • 70
    • 83

    Rain Showers Likely

    • 65
    • 85

    Chance Rain Showers

Today 4 Sep Jefferson

Warm and humid. Mostly cloudy in the morning then becoming partly sunny. Chance of light Showers and Thunderstorms in the morning. Slight chance of light Showers and Thunderstorms late in the afternoon. Highs in the upper 80s. Southwest Winds 5 to 10 Mph. Chance of precipitation 30 percent. Highest heat index Readings 95 to 98 in the afternoon.

Tonight 4 Sep Jefferson

Partly cloudy. A 50 percent chance of light Showers and Thunderstorms through around midnight. Patchy fog early in the morning. Lows in the upper 60s. Southwest Winds up to 5 Mph shifting to the north after midnight.

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  • Temperature Real-Time

Lake Koshkonong Temperature Statistics

September Temperature

Watertown (20.5 miles)

  • Lowest 1 September, 2026

    67.6 °F

  • Average September

    76.7 °F

  • Highest 1 September, 2026

    87.3 °F

Climate (2021–2026)

Watertown (20.5 miles)

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  • Average Low 2021–2026

    35.2 °F

  • Average 2021–2026

    44.8 °F

  • Average High 2021–2026

    53.9 °F
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