South Mountain Reservoir Weather Forecast

    • 48
    • 76

    Mostly Cloudy

    • 41
    • 68

    Becoming Sunny

    • 46
    • 75

    Sunny

    • 49
    • 81

    Sunny

    • 46
    • 80

    Mostly Sunny

    • 47
    • 77

    Partly Sunny

    • 46
    • 75

    Mostly Sunny

Today 13 Sep Modoc County

Sunny. Highs in the mid 70s to lower 80s. Southeast Winds around 5 Mph shifting to the southwest this afternoon.

Tonight 13 Sep Modoc County

Mostly cloudy early this evening then becoming partly cloudy. Isolated Thunderstorms well after midnight. Lows in the mid 40s to lower 50s. Southwest Winds 5 to 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 11 September, 2025

    42.1 °F

  • Average September

    67.6 °F

  • Highest 1 September, 2025

    91 °F

Climate (2020–Present)

Alturas (22.4 miles)

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  • Average Low 2020–2025

    32.9 °F

  • Average 2020–2025

    49.2 °F

  • Average High 2020–2025

    64.4 °F
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