National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce
Current conditions at

Islip, Long Island Mac Arthur Airport (KISP)

Lat: 40.79°NLon: 73.1°WElev: 98ft.

A Few Clouds

20°F

-7°C

Humidity 38%
Wind Speed W 9 mph
Barometer 30.34 in (1027.4 mb)
Dewpoint -2°F (-19°C)
Visibility 10.00 mi
Wind Chill10°F (-12°C)
Last update 20 Jan 4:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly clear, with a low around 17. Wind chill values between 5 and 10. Breezy, with a west wind 11 to 20 mph.

    Low: 17 °F

    Mostly Clear
    and Breezy
    then Mostly
    Clear

  • Wednesday

    Wednesday: Increasing clouds, with a high near 38. Wind chill values between 5 and 15. South wind 9 to 16 mph.

    High: 38 °F

    Increasing
    Clouds

  • Wednesday Night

    Wednesday Night: A slight chance of rain and snow before 1am, then a slight chance of snow between 1am and 4am, then a slight chance of rain after 4am. Cloudy, then gradually becoming partly cloudy, with a low around 35. Southwest wind 16 to 18 mph. Chance of precipitation is 20%.

    Low: 35 °F

    Slight Chance
    Rain/Snow

  • Thursday

    Thursday: Mostly sunny, with a high near 42. West wind 16 to 18 mph.

    High: 42 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Mostly cloudy, with a low around 25. West wind 14 to 18 mph.

    Low: 25 °F

    Mostly Cloudy

  • Friday

    Friday: Partly sunny, with a high near 32. Breezy.

    High: 32 °F

    Partly Sunny
    then Mostly
    Cloudy and
    Breezy

  • Friday Night

    Friday Night: Partly cloudy, with a low around 12. Blustery.

    Low: 12 °F

    Partly Cloudy
    and Blustery

  • Saturday

    Saturday: Partly sunny and cold, with a high near 18.

    High: 18 °F

    Cold

  • Saturday Night

    Saturday Night: A 40 percent chance of snow after 1am. Mostly cloudy, with a low around 14.

    Low: 14 °F

    Mostly Cloudy
    then Chance
    Snow

Detailed Forecast

Tonight
Mostly clear, with a low around 17. Wind chill values between 5 and 10. Breezy, with a west wind 11 to 20 mph.
Wednesday
Increasing clouds, with a high near 38. Wind chill values between 5 and 15. South wind 9 to 16 mph.
Wednesday Night
A slight chance of rain and snow before 1am, then a slight chance of snow between 1am and 4am, then a slight chance of rain after 4am. Cloudy, then gradually becoming partly cloudy, with a low around 35. Southwest wind 16 to 18 mph. Chance of precipitation is 20%.
Thursday
Mostly sunny, with a high near 42. West wind 16 to 18 mph.
Thursday Night
Mostly cloudy, with a low around 25. West wind 14 to 18 mph.
Friday
Partly sunny, with a high near 32. Breezy.
Friday Night
Partly cloudy, with a low around 12. Blustery.
Saturday
Partly sunny and cold, with a high near 18.
Saturday Night
A 40 percent chance of snow after 1am. Mostly cloudy, with a low around 14.
Sunday
A 50 percent chance of snow. Cloudy, with a high near 21.
Sunday Night
A 50 percent chance of snow. Mostly cloudy, with a low around 18.
Monday
A 30 percent chance of snow. Partly sunny, with a high near 25.
Monday Night
Partly cloudy, with a low around 17.
Tuesday
Mostly sunny, with a high near 26.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
3:33 pm EST Jan 20, 2026
Forecast Valid:
5pm EST Jan 20, 2026-6pm EST Jan 27, 2026
 
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Additional Resources

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Chance of Precipitation