South Mountain Reservoir Weather Forecast

    • 45
    • 77

    Becoming Sunny

    • 49
    • 79

    Mostly Cloudy

    • 37
    • 64

    Mostly Sunny

    • 42
    • 68

    Partly Sunny

    • 36
    • 65

    Partly Sunny

    • 37
    • 64

    Mostly Sunny

    • 39
    • 69

    Mostly Sunny

Today 23 Sep Modoc County

Sunny. Highs in the mid 70s to lower 80s. East Winds around 5 Mph shifting to the southeast late this Morning, then shifting to the southwest this afternoon.

Tonight 23 Sep Modoc County

Partly cloudy early this evening then clearing. Lows in the mid 40s to lower 50s. West Winds around 5 Mph shifting to the southeast after midnight.

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South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 14 September, 2026

    28.7 °F

  • Average September

    58.7 °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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