San Clemente Island - Northwest Harbor Weather Forecast

    • 65
    • 73

    Increasing Clouds

    • 65
    • 74

    Chance Rain Showers

    • 65
    • 73

    Chance Thunderstorms

    • 64
    • 72

    Slight Chance Thunderstorms

    • 64
    • 72

    Mostly Cloudy

    • 65
    • 73

    Patchy Fog

    • 65
    • 73

    Partly Sunny

Today 16 Sep Catalina and Santa Barbara Islands

Sunny after morning low Clouds and fog. Highs from the mid 70s to around 80 near the coast to the mid 80s interior.

Tonight 16 Sep Catalina and Santa Barbara Islands

Mostly clear in the evening then cloudy. Lows in the 60s to around 70.

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San Clemente Island - Northwest Harbor Temperature Statistics

September Temperature

San Clemente Island NALF (0.6 miles)

  • Lowest 5 September, 2025

    62.1 °F

  • Average September

    67 °F

  • Highest 7 September, 2025

    75 °F

Climate (2020–Present)

San Clemente Island NALF (0.6 miles)

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  • Average Low 2020–2025

    56.8 °F

  • Average 2020–2025

    61.3 °F

  • Average High 2020–2025

    66.1 °F
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