South Mountain Reservoir Weather Forecast

    • 41
    • 68

    Becoming Sunny

    • 43
    • 73

    Mostly Sunny

    • 46
    • 78

    Mostly Sunny

    • 46
    • 78

    Mostly Sunny

    • 44
    • 78

    Mostly Sunny

    • 46
    • 78

    Mostly Sunny

Today 18 Sep Modoc County

Mostly cloudy then becoming partly cloudy late this morning then becoming sunny. Highs in the mid 60s to lower 70s. North Winds 5 to 10 Mph.

Tonight 18 Sep Modoc County

Mostly clear. Lows in the lower to mid 40s. North Winds 5 to 10 Mph shifting to the northeast well after midnight.

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South Mountain Reservoir Temperature Statistics

September Temperature

Alturas (22.4 miles)

  • Lowest 14 September, 2026

    32 °F

  • Average September

    60.9 °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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