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.

Fair

34°F

1°C

Humidity 82%
Wind Speed S 5 mph
Barometer 29.74 in (1007.0 mb)
Dewpoint 29°F (-2°C)
Visibility 9.00 mi
Wind Chill29°F (-2°C)
Last update 26 Feb 1:56 am EST
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Mostly clear, with a low around 30. West wind around 8 mph.

    Low: 30 °F

    Mostly Clear

  • Thursday

    Thursday: A 20 percent chance of snow after 1pm. Partly sunny, with a high near 36. Wind chill values between 25 and 35. Northwest wind 3 to 6 mph.

    High: 36 °F

    Mostly Sunny
    then Slight
    Chance Snow

  • Thursday Night

    Thursday Night: Mostly cloudy, then gradually becoming mostly clear, with a low around 22. Light north wind.

    Low: 22 °F

    Decreasing
    Clouds

  • Friday

    Friday: Sunny, with a high near 37. Wind chill values between 25 and 35. Calm wind becoming southwest around 5 mph.

    High: 37 °F

    Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 28. Light south wind.

    Low: 28 °F

    Mostly Clear

  • Saturday

    Saturday: Sunny, with a high near 44.

    High: 44 °F

    Sunny

  • Saturday Night

    Saturday Night: Increasing clouds, with a low around 28.

    Low: 28 °F

    Increasing
    Clouds

  • Sunday

    Sunday: Mostly cloudy, with a high near 36.

    High: 36 °F

    Mostly Cloudy

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 17.

    Low: 17 °F

    Partly Cloudy

Detailed Forecast

Overnight
Mostly clear, with a low around 30. West wind around 8 mph.
Thursday
A 20 percent chance of snow after 1pm. Partly sunny, with a high near 36. Wind chill values between 25 and 35. Northwest wind 3 to 6 mph.
Thursday Night
Mostly cloudy, then gradually becoming mostly clear, with a low around 22. Light north wind.
Friday
Sunny, with a high near 37. Wind chill values between 25 and 35. Calm wind becoming southwest around 5 mph.
Friday Night
Mostly clear, with a low around 28. Light south wind.
Saturday
Sunny, with a high near 44.
Saturday Night
Increasing clouds, with a low around 28.
Sunday
Mostly cloudy, with a high near 36.
Sunday Night
Partly cloudy, with a low around 17.
Monday
A 30 percent chance of snow. Mostly cloudy, with a high near 26.
Monday Night
Mostly cloudy, with a low around 18.
Tuesday
Mostly cloudy, with a high near 34.
Tuesday Night
A 50 percent chance of snow. Cloudy, with a low around 27.
Wednesday
A 50 percent chance of rain. Partly sunny, with a high near 40.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.93°N 73.06°W (Elev. 161 ft)
Last Update:
12:57 am EST Feb 26, 2026
Forecast Valid:
2am EST Feb 26, 2026-6pm EST Mar 4, 2026
 
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Additional Resources

Radar & Satellite Image

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Hourly Weather Forecast

National Digital Forecast Database

National Digital Forecast Database Maximum Temperature Forecast

High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation