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

23°F

-5°C

Humidity 38%
Wind Speed N 9 mph
Barometer 30.25 in (1024.3 mb)
Dewpoint 1°F (-17°C)
Visibility 10.00 mi
Wind Chill13°F (-11°C)
Last update 9 Dec 1:56 am EST
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Partly cloudy, with a low around 20. Wind chill values between 10 and 15. North wind around 9 mph.

    Low: 20 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Increasing clouds, with a high near 36. Wind chill values between 10 and 20. North wind 5 to 7 mph becoming south in the afternoon.

    High: 36 °F

    Increasing
    Clouds

  • Tuesday Night

    Tuesday Night: A 20 percent chance of snow before 10pm. Mostly cloudy, with a low around 31. Wind chill values between 25 and 30. Southwest wind 10 to 15 mph.

    Low: 31 °F

    Slight Chance
    Snow then
    Mostly Cloudy

  • Wednesday

    Wednesday: Rain likely, mainly after 1pm. Mostly cloudy, with a high near 47. Wind chill values between 25 and 35 early. Breezy, with a southwest wind 13 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

    High: 47 °F

    Slight Chance
    Rain then
    Rain Likely
    and Breezy

  • Wednesday Night

    Wednesday Night: A 30 percent chance of rain before 1am. Cloudy, then gradually becoming partly cloudy, with a low around 32. Southwest wind 15 to 18 mph.

    Low: 32 °F

    Chance Rain

  • Thursday

    Thursday: Mostly sunny, with a high near 39. Breezy.

    High: 39 °F

    Mostly Sunny
    then Mostly
    Sunny and
    Breezy

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 28. Breezy.

    Low: 28 °F

    Partly Cloudy
    and Breezy
    then Partly
    Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 37.

    High: 37 °F

    Mostly Sunny

  • Friday Night

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

    Low: 29 °F

    Mostly Cloudy
    then Chance
    Snow

Detailed Forecast

Overnight
Partly cloudy, with a low around 20. Wind chill values between 10 and 15. North wind around 9 mph.
Tuesday
Increasing clouds, with a high near 36. Wind chill values between 10 and 20. North wind 5 to 7 mph becoming south in the afternoon.
Tuesday Night
A 20 percent chance of snow before 10pm. Mostly cloudy, with a low around 31. Wind chill values between 25 and 30. Southwest wind 10 to 15 mph.
Wednesday
Rain likely, mainly after 1pm. Mostly cloudy, with a high near 47. Wind chill values between 25 and 35 early. Breezy, with a southwest wind 13 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.
Wednesday Night
A 30 percent chance of rain before 1am. Cloudy, then gradually becoming partly cloudy, with a low around 32. Southwest wind 15 to 18 mph.
Thursday
Mostly sunny, with a high near 39. Breezy.
Thursday Night
Partly cloudy, with a low around 28. Breezy.
Friday
Mostly sunny, with a high near 37.
Friday Night
A 30 percent chance of snow after 1am. Mostly cloudy, with a low around 29.
Saturday
Partly sunny, with a high near 40.
Saturday Night
A 30 percent chance of snow. Mostly cloudy, with a low around 27.
Sunday
A 30 percent chance of snow. Partly sunny, with a high near 33.
Sunday Night
Partly cloudy, with a low around 20.
Monday
Mostly sunny, with a high near 29.
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:
1:43 am EST Dec 9, 2025
Forecast Valid:
2am EST Dec 9, 2025-6pm EST Dec 15, 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