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.

A Few Clouds

42°F

6°C

Humidity 40%
Wind Speed NW 10 mph
Barometer 30.20 in (1022.8 mb)
Dewpoint 19°F (-7°C)
Visibility 10.00 mi
Wind Chill36°F (2°C)
Last update 14 Mar 7:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Increasing clouds, with a low around 34. Northwest wind 13 to 18 mph decreasing to 6 to 11 mph after midnight.

    Low: 34 °F

    Increasing
    Clouds

  • Sunday

    Sunday: Partly sunny, with a high near 46. Northeast wind 7 to 13 mph becoming southeast in the afternoon.

    High: 46 °F

    Partly Sunny

  • Sunday Night

    Sunday Night: Showers after 2am. Temperature falling to near 41 by 9pm, then rising to around 49 during the remainder of the night. Southeast wind 10 to 17 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 41 °F⇑

    Mostly Cloudy
    then Showers

  • Monday

    Monday: Showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 56. Windy, with a south wind 23 to 28 mph, with gusts as high as 39 mph. Chance of precipitation is 100%. New rainfall amounts between a half and three quarters of an inch possible.

    High: 56 °F

    Heavy Rain
    and Windy

  • Monday Night

    Monday Night: Showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 36. Windy, with a south wind 31 to 37 mph, with gusts as high as 49 mph. Chance of precipitation is 100%. New precipitation amounts between a half and three quarters of an inch possible.

    Low: 36 °F

    Heavy Rain
    and Windy

  • Tuesday

    Tuesday: A 30 percent chance of showers before 8am. Mostly sunny, with a high near 40. Breezy.

    High: 40 °F

    Breezy.
    Chance
    Showers then
    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 27. Breezy.

    Low: 27 °F

    Partly Cloudy
    and Breezy
    then Mostly
    Clear

  • Wednesday

    Wednesday: Mostly sunny, with a high near 37.

    High: 37 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 32.

    Low: 32 °F

    Mostly Cloudy

Detailed Forecast

Tonight
Increasing clouds, with a low around 34. Northwest wind 13 to 18 mph decreasing to 6 to 11 mph after midnight.
Sunday
Partly sunny, with a high near 46. Northeast wind 7 to 13 mph becoming southeast in the afternoon.
Sunday Night
Showers after 2am. Temperature falling to near 41 by 9pm, then rising to around 49 during the remainder of the night. Southeast wind 10 to 17 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Monday
Showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 56. Windy, with a south wind 23 to 28 mph, with gusts as high as 39 mph. Chance of precipitation is 100%. New rainfall amounts between a half and three quarters of an inch possible.
Monday Night
Showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 36. Windy, with a south wind 31 to 37 mph, with gusts as high as 49 mph. Chance of precipitation is 100%. New precipitation amounts between a half and three quarters of an inch possible.
Tuesday
A 30 percent chance of showers before 8am. Mostly sunny, with a high near 40. Breezy.
Tuesday Night
Partly cloudy, with a low around 27. Breezy.
Wednesday
Mostly sunny, with a high near 37.
Wednesday Night
Mostly cloudy, with a low around 32.
Thursday
Mostly sunny, with a high near 43.
Thursday Night
Mostly cloudy, with a low around 35.
Friday
Mostly sunny, with a high near 46.
Friday Night
A 30 percent chance of rain. Partly cloudy, with a low around 37.
Saturday
A 30 percent chance of rain. Partly sunny, with a high near 45.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
7:50 pm EDT Mar 14, 2026
Forecast Valid:
8pm EDT Mar 14, 2026-6pm EDT Mar 21, 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