Jefferson Weather Forecast

    • 20
    • 41

    Mostly Sunny

    • 32
    • 44

    Mostly Cloudy

    • 29
    • 53

    Partly Sunny

    • 32
    • 45

    Mostly Cloudy

    • 36
    • 51

    Mostly Cloudy

    • 29
    • 58

    Partly Sunny

    • 26
    • 47

    Mostly Cloudy

Today 20 Dec Union

Sunny. Highs in the upper 30s. Northwest Winds 10 to 15 Mph.

Tonight 20 Dec Union

Mostly clear. Cooler with Lows around 18. Northeast Winds around 5 Mph, becoming southeast after midnight.

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Jefferson Temperature Statistics

December Temperature

Sioux City, Sioux Gateway Airport (16.2 miles)

  • Lowest 14 December, 2025

    -11.9 °F

  • Average December

    21.7 °F

  • Highest 9 December, 2025

    48 °F

Climate (2020–Present)

Sioux City, Sioux Gateway Airport (16.2 miles)

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  • Average Low 2020–2025

    39 °F

  • Average 2020–2025

    50.8 °F

  • Average High 2020–2025

    62.7 °F
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