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.

Partly Cloudy

42°F

6°C

Humidity 62%
Wind Speed Calm
Barometer 30.12 in (1019.9 mb)
Dewpoint 30°F (-1°C)
Visibility 10.00 mi
Last update 7 Dec 9:56 am EST
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Partly sunny, with a high near 42. North wind around 6 mph becoming southwest in the afternoon.

    High: 42 °F

    Partly Sunny

  • Tonight

    Tonight: Partly cloudy, with a low around 25. Wind chill values between 15 and 20. Southwest wind 8 to 18 mph becoming northwest after midnight.

    Low: 25 °F

    Partly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 31. Wind chill values between 10 and 20. Blustery, with a north wind 13 to 21 mph.

    High: 31 °F

    Sunny and
    Blustery then
    Partly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 18. Wind chill values between 10 and 15. North wind 6 to 11 mph.

    Low: 18 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Increasing clouds, with a high near 39. Light and variable wind becoming south 5 to 10 mph in the morning.

    High: 39 °F

    Increasing
    Clouds

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a steady temperature around 36.

    Low: 36 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: A 40 percent chance of rain. Cloudy, with a high near 47.

    High: 47 °F

    Chance Rain

  • Wednesday Night

    Wednesday Night: A 30 percent chance of rain before 1am. Mostly cloudy, with a low around 36.

    Low: 36 °F

    Chance Rain

  • Thursday

    Thursday: Mostly sunny, with a high near 43.

    High: 43 °F

    Mostly Sunny

Detailed Forecast

Today
Partly sunny, with a high near 42. North wind around 6 mph becoming southwest in the afternoon.
Tonight
Partly cloudy, with a low around 25. Wind chill values between 15 and 20. Southwest wind 8 to 18 mph becoming northwest after midnight.
Monday
Mostly sunny, with a high near 31. Wind chill values between 10 and 20. Blustery, with a north wind 13 to 21 mph.
Monday Night
Partly cloudy, with a low around 18. Wind chill values between 10 and 15. North wind 6 to 11 mph.
Tuesday
Increasing clouds, with a high near 39. Light and variable wind becoming south 5 to 10 mph in the morning.
Tuesday Night
Mostly cloudy, with a steady temperature around 36.
Wednesday
A 40 percent chance of rain. Cloudy, with a high near 47.
Wednesday Night
A 30 percent chance of rain before 1am. Mostly cloudy, with a low around 36.
Thursday
Mostly sunny, with a high near 43.
Thursday Night
A chance of rain and snow after 1am. Mostly cloudy, with a low around 32. Chance of precipitation is 30%.
Friday
A chance of rain and snow. Mostly cloudy, with a high near 39. Chance of precipitation is 40%.
Friday Night
A chance of rain and snow. Mostly cloudy, with a low around 26. Chance of precipitation is 40%.
Saturday
A 30 percent chance of snow. Partly sunny, with a high near 33.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
7:42 am EST Dec 7, 2025
Forecast Valid:
10am EST Dec 7, 2025-6pm EST Dec 13, 2025
 
Forecast Discussion
 
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Additional Resources

Radar & Satellite Image

Link to Local Radar Data Link to Satellite Data

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