Janesville Weather Forecast

    • 10
    • 23

    Mostly Cloudy

    • 25
    • 34

    Mostly Cloudy

    • 30
    • 35

    Rain Likely

    • 4
    • 40

    Slight Chance Rain/Snow

    • 18
    • 26

    Mostly Cloudy

    • 16
    • 37

    Mostly Cloudy

Today 15 Dec Rock

Not as cold. Mostly cloudy. Highs in the lower 20s. Southwest Winds 5 to 15 Mph.

Tonight 15 Dec Rock

Partly cloudy until early morning then becoming mostly cloudy. Patchy fog after midnight. Lows around 10. South Winds up to 5 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Janesville Temperature Statistics

December Temperature

Janesville-Rock County (4.3 miles)

  • Lowest 4 December, 2025

    -5.8 °F

  • Average December

    18.8 °F

  • Highest 10 December, 2025

    37.4 °F

Climate (2020–Present)

Janesville-Rock County (4.3 miles)

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  • Average Low 2020–2025

    40.4 °F

  • Average 2020–2025

    48.7 °F

  • Average High 2020–2025

    60.2 °F
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