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

20°F

-7°C

Humidity 55%
Wind Speed Calm
Barometer 30.16 in (1021.6 mb)
Dewpoint 6°F (-14°C)
Visibility 10.00 mi
Last update 9 Feb 11:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Mostly cloudy, with a low around 18. Light northwest wind.

    Low: 18 °F

    Mostly Cloudy

  • Tuesday

    Tuesday: A 20 percent chance of snow after 1pm. Mostly cloudy, with a high near 35. Wind chill values between 20 and 30. Calm wind becoming south around 6 mph in the afternoon.

    High: 35 °F

    Partly Sunny
    then Slight
    Chance Snow

  • Tuesday Night

    Tuesday Night: A chance of rain before 1am, then a slight chance of freezing rain between 1am and 4am, then a slight chance of snow after 4am. Cloudy, then gradually becoming partly cloudy, with a steady temperature around 32. Light and variable wind becoming west around 6 mph after midnight. Chance of precipitation is 50%.

    Low: 32 °F

    Chance Rain
    then Chance
    Wintry Mix

  • Wednesday

    Wednesday: Mostly sunny, with a high near 37. Wind chill values between 25 and 30. West wind 7 to 13 mph.

    High: 37 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 23. West wind around 11 mph, with gusts as high as 21 mph.

    Low: 23 °F

    Partly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 33.

    High: 33 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 19.

    Low: 19 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 32.

    High: 32 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 20.

    Low: 20 °F

    Mostly Clear

Detailed Forecast

Overnight
Mostly cloudy, with a low around 18. Light northwest wind.
Tuesday
A 20 percent chance of snow after 1pm. Mostly cloudy, with a high near 35. Wind chill values between 20 and 30. Calm wind becoming south around 6 mph in the afternoon.
Tuesday Night
A chance of rain before 1am, then a slight chance of freezing rain between 1am and 4am, then a slight chance of snow after 4am. Cloudy, then gradually becoming partly cloudy, with a steady temperature around 32. Light and variable wind becoming west around 6 mph after midnight. Chance of precipitation is 50%.
Wednesday
Mostly sunny, with a high near 37. Wind chill values between 25 and 30. West wind 7 to 13 mph.
Wednesday Night
Partly cloudy, with a low around 23. West wind around 11 mph, with gusts as high as 21 mph.
Thursday
Mostly sunny, with a high near 33.
Thursday Night
Partly cloudy, with a low around 19.
Friday
Mostly sunny, with a high near 32.
Friday Night
Mostly clear, with a low around 20.
Saturday
Sunny, with a high near 34.
Saturday Night
Partly cloudy, with a low around 23.
Sunday
A chance of rain and snow. Mostly cloudy, with a high near 36. Chance of precipitation is 40%.
Sunday Night
Rain likely. Cloudy, with a low around 29. Chance of precipitation is 70%.
Washington's Birthday
Rain likely. Mostly cloudy, with a high near 39. Chance of precipitation is 60%.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.93°N 73.06°W (Elev. 161 ft)
Last Update:
11:17 pm EST Feb 9, 2026
Forecast Valid:
12am EST Feb 10, 2026-6pm EST Feb 16, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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