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.

Overcast

41°F

5°C

Humidity 55%
Wind Speed W 10 mph
Barometer 30.03 in (1016.9 mb)
Dewpoint 26°F (-3°C)
Visibility 10.00 mi
Wind Chill35°F (2°C)
Last update 7 Dec 6:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly cloudy, then gradually becoming mostly clear, with a low around 24. West wind 10 to 17 mph becoming northwest after midnight.

    Low: 24 °F

    Decreasing
    Clouds

  • Monday

    Monday: Mostly sunny, with a high near 30. Wind chill values between 15 and 20. North wind 11 to 18 mph, with gusts as high as 29 mph.

    High: 30 °F

    Mostly Sunny

  • Monday Night

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

    Low: 18 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Increasing clouds, with a high near 41. Wind chill values between 20 and 30. Light and variable wind becoming south 5 to 10 mph in the morning.

    High: 41 °F

    Increasing
    Clouds

  • Tuesday Night

    Tuesday Night: A slight chance of rain before 1am, then a slight chance of rain and snow. Mostly cloudy, with a steady temperature around 37. Southwest wind 13 to 16 mph. Chance of precipitation is 20%.

    Low: 37 °F

    Slight Chance
    Rain then
    Slight Chance
    Rain/Snow

  • Wednesday

    Wednesday: A 50 percent chance of rain. Mostly cloudy, with a high near 47.

    High: 47 °F

    Chance Rain

  • Wednesday Night

    Wednesday Night: A 30 percent chance of rain before 1am. Cloudy, then gradually becoming partly cloudy, with a low around 36.

    Low: 36 °F

    Chance Rain

  • Thursday

    Thursday: Mostly sunny, with a high near 42.

    High: 42 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: A 30 percent chance of rain after 1am. Mostly cloudy, with a low around 29.

    Low: 29 °F

    Mostly Cloudy
    then Chance
    Rain

Detailed Forecast

Tonight
Mostly cloudy, then gradually becoming mostly clear, with a low around 24. West wind 10 to 17 mph becoming northwest after midnight.
Monday
Mostly sunny, with a high near 30. Wind chill values between 15 and 20. North wind 11 to 18 mph, with gusts as high as 29 mph.
Monday Night
Partly cloudy, with a low around 18. Wind chill values between 10 and 15. North wind 6 to 10 mph.
Tuesday
Increasing clouds, with a high near 41. Wind chill values between 20 and 30. Light and variable wind becoming south 5 to 10 mph in the morning.
Tuesday Night
A slight chance of rain before 1am, then a slight chance of rain and snow. Mostly cloudy, with a steady temperature around 37. Southwest wind 13 to 16 mph. Chance of precipitation is 20%.
Wednesday
A 50 percent chance of rain. Mostly cloudy, with a high near 47.
Wednesday Night
A 30 percent chance of rain before 1am. Cloudy, then gradually becoming partly cloudy, with a low around 36.
Thursday
Mostly sunny, with a high near 42.
Thursday Night
A 30 percent chance of rain after 1am. Mostly cloudy, with a low around 29.
Friday
A 30 percent chance of rain. Partly sunny, with a high near 38.
Friday Night
A chance of rain and snow. Mostly cloudy, with a low around 26. Chance of precipitation is 30%.
Saturday
A 30 percent chance of snow. Partly sunny, with a high near 35.
Saturday Night
Partly cloudy, with a low around 23.
Sunday
Mostly sunny, with a high near 33.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
5:39 pm EST Dec 7, 2025
Forecast Valid:
7pm EST Dec 7, 2025-6pm EST Dec 14, 2025
 
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