Port Jefferson Harbor Weather Forecast

    • 68
    • 77

    Rain Showers

    • 61
    • 73

    Mostly Sunny

    • 60
    • 70

    Mostly Sunny

    • 65
    • 75

    Partly Sunny

    • 67
    • 78

    Partly Sunny

    • 63
    • 77

    Chance Rain Showers

Today 13 Sep Northwest Suffolk

Showers with a chance of Thunderstorms this Morning, then Showers likely with a slight chance of Thunderstorms this afternoon. Locally heavy rainfall possible. Highs in the upper 70s. Southeast Winds 5 to 10 Mph, becoming northwest this afternoon. Chance of rain near 100 percent.

Tonight 13 Sep Northwest Suffolk

Partly cloudy. Humid with Lows in the mid 60s. West Winds 5 to 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Port Jefferson Harbor Temperature Statistics

September Temperature

Islip, Long Island Mac Arthur Airport (11.2 miles)

  • Lowest 7 September, 2026

    56.6 °F

  • Average September

    72.8 °F

  • Highest 3 September, 2026

    85.6 °F

Climate (2021–2026)

Islip, Long Island Mac Arthur Airport (11.2 miles)

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  • Average Low 2021–2026

    47.3 °F

  • Average 2021–2026

    55.2 °F

  • Average High 2021–2026

    63.1 °F
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