South Mountain Reservoir Weather Forecast

    • 38
    • 65

    Gradual Clearing

    • 38
    • 68

    Mostly Sunny

    • 41
    • 73

    Sunny

    • 43
    • 77

    Sunny

    • 44
    • 78

    Partly Sunny

    • 41
    • 73

    Mostly Sunny

Today 27 Sep Modoc County

Mostly cloudy. Isolated Showers this afternoon. Highs in the mid 60s to lower 70s. Southeast Winds 10 to 15 Mph shifting to the southwest late this afternoon.

Tonight 27 Sep Modoc County

Partly cloudy with isolated Showers in the Evening, then mostly clear after midnight. Lows in the mid 30s to lower 40s. West Winds 5 to 10 Mph shifting to the northwest well after midnight.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 14 September, 2026

    28.7 °F

  • Average September

    58.8 °F

  • Highest 24 September, 2026

    86.6 °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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