South Mountain Reservoir Weather Forecast

    • 42
    • 75

    Mostly Sunny

    • 46
    • 78

    Partly Sunny

    • 48
    • 78

    Partly Sunny

    • 36
    • 64

    Slight Chance Rain

    • 40
    • 66

    Partly Sunny

    • 36
    • 64

    Mostly Sunny

Today 22 Sep Modoc County

Sunny early this afternoon then becoming partly cloudy. Highs in the mid 70s to lower 80s. West Winds 5 to 10 Mph.

Tonight 22 Sep Modoc County

Mostly clear. Scattered Showers and isolated Thunderstorms early this evening. Lows in the lower to mid 40s. Northwest Winds 5 to 10 Mph shifting to the north after midnight. Chance of precipitation 30 percent.

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South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 14 September, 2026

    28.7 °F

  • Average September

    59.4 °F

  • Highest 10 September, 2026

    85.6 °F

Climate (2021–2026)

Alturas (22.4 miles)

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  • Average Low 2021–2026

    33.2 °F

  • Average 2021–2026

    49.1 °F

  • Average High 2021–2026

    64.7 °F
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