South Mountain Reservoir Weather Forecast

    • 43
    • 70

    Chance Rain Showers

    • 42
    • 66

    Chance Rain Showers

    • 43
    • 70

    Mostly Sunny

    • 45
    • 75

    Mostly Sunny

    • 46
    • 77

    Mostly Sunny

    • 46
    • 77

    Mostly Sunny

Today 16 Sep Modoc County

Partly cloudy with a 20 percent chance of Thunderstorms. Highs in the mid 60s to mid 70s. Northeast Winds 5 to 10 Mph shifting to the southeast in the afternoon.

Tonight 16 Sep Modoc County

Partly cloudy in the evening then becoming mostly cloudy. Slight chance of Thunderstorms. Lows in the lower to mid 40s. Southeast Winds 5 to 10 Mph shifting to the northwest in the late evening and early Morning, then shifting to the east well after midnight.

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South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 13 September, 2026

    36 °F

  • Average September

    61.5 °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

    64.6 °F
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