South Mountain Reservoir Weather Forecast

    • 36
    • 49

    Decreasing Clouds

    • 38
    • 51

    Partly Sunny

    • 39
    • 53

    Mostly Cloudy

    • 39
    • 53

    Mostly Cloudy

    • 35
    • 54

    Mostly Sunny

    • 31
    • 56

    Sunny

Today 7 Dec Modoc County

Partly cloudy then becoming mostly cloudy early this afternoon then becoming partly cloudy. Highs in the mid 40s to lower 50s. Southwest Winds 10 to 15 Mph shifting to the west late this afternoon.

Tonight 7 Dec Modoc County

Mostly clear in the evening then becoming partly cloudy. Lows in the mid 30s to lower 40s. Southwest Winds 5 to 10 Mph shifting to the south late in the evening and overnight.

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South Mountain Reservoir Temperature Statistics

December Temperature

Alturas (22.4 miles)

  • Lowest 1 December, 2025

    15.1 °F

  • Average December

    35.4 °F

  • Highest 1 December, 2025

    51.1 °F

Climate (2020–Present)

Alturas (22.4 miles)

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  • Average Low 2020–2025

    33.2 °F

  • Average 2020–2025

    49.2 °F

  • Average High 2020–2025

    64.3 °F
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