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.

Mostly Cloudy

72°F

22°C

Humidity 73%
Wind Speed S 3 mph
Barometer 30.05 in (1017.6 mb)
Dewpoint 63°F (17°C)
Visibility 10.00 mi
Last update 26 Aug 7:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly cloudy, with a low around 70. South wind around 8 mph.

    Low: 70 °F

    Mostly Cloudy

  • Thursday

    Thursday: A 40 percent chance of showers and thunderstorms after 11am. Partly sunny, with a high near 80. South wind 7 to 14 mph.

    High: 80 °F

    Chance
    Showers

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 69. South wind 5 to 10 mph becoming light after midnight. Chance of precipitation is 50%.

    Low: 69 °F

    Chance
    Showers

  • Friday

    Friday: A slight chance of showers before 8am, then a slight chance of showers after 2pm. Partly sunny, with a high near 82. West wind 3 to 5 mph. Chance of precipitation is 20%.

    High: 82 °F

    Partly Sunny
    then Slight
    Chance
    Showers

  • Friday Night

    Friday Night: Partly cloudy, with a low around 66. West wind 5 to 9 mph becoming north after midnight.

    Low: 66 °F

    Partly Cloudy

  • Saturday

    Saturday: Sunny, with a high near 77.

    High: 77 °F

    Sunny

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 67.

    Low: 67 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny, with a high near 80.

    High: 80 °F

    Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 71.

    Low: 71 °F

    Partly Cloudy

Detailed Forecast

Tonight
Mostly cloudy, with a low around 70. South wind around 8 mph.
Thursday
A 40 percent chance of showers and thunderstorms after 11am. Partly sunny, with a high near 80. South wind 7 to 14 mph.
Thursday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 69. South wind 5 to 10 mph becoming light after midnight. Chance of precipitation is 50%.
Friday
A slight chance of showers before 8am, then a slight chance of showers after 2pm. Partly sunny, with a high near 82. West wind 3 to 5 mph. Chance of precipitation is 20%.
Friday Night
Partly cloudy, with a low around 66. West wind 5 to 9 mph becoming north after midnight.
Saturday
Sunny, with a high near 77.
Saturday Night
Mostly clear, with a low around 67.
Sunday
Sunny, with a high near 80.
Sunday Night
Partly cloudy, with a low around 71.
Monday
Mostly sunny, with a high near 81.
Monday Night
Partly cloudy, with a low around 71.
Tuesday
Mostly sunny, with a high near 81.
Tuesday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 71.
Wednesday
A 30 percent chance of showers. Partly sunny, with a high near 81.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
2:53 pm EDT Aug 26, 2026
Forecast Valid:
8pm EDT Aug 26, 2026-6pm EDT Sep 2, 2026
 
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