South Mountain Reservoir Weather Forecast

    • 44
    • 75

    Mostly Sunny

    • 43
    • 69

    Partly Sunny

    • 42
    • 69

    Slight Chance Thunderstorms

    • 44
    • 72

    Sunny

    • 45
    • 76

    Mostly Sunny

    • 46
    • 79

    Mostly Sunny

Today 15 Sep Modoc County

Sunny. Highs in the lower 70s to lower 80s. East Winds around 5 Mph shifting to the southwest 10 to 15 Mph in the afternoon.

Tonight 15 Sep Modoc County

Mostly clear. A 10 percent chance of Showers after midnight. Lows in the lower to mid 40s. Northwest Winds 10 to 15 Mph shifting to the north 5 to 10 Mph well after midnight.

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South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 11 September, 2026

    36.6 °F

  • Average September

    65.1 °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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