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

72°F

22°C

Humidity 44%
Wind Speed E 6 mph
Barometer 30.26 in (1024.6 mb)
Dewpoint 49°F (9°C)
Visibility 10.00 mi
Last update 20 Sep 12:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • This Afternoon

    This Afternoon: Sunny, with a high near 71. East wind around 10 mph.

    High: 71 °F

    Sunny

  • Tonight

    Tonight: Partly cloudy, with a low around 55. Southeast wind around 7 mph.

    Low: 55 °F

    Partly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 69. East wind around 10 mph.

    High: 69 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 54. East wind 6 to 8 mph.

    Low: 54 °F

    Partly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 73. Northeast wind around 6 mph becoming southeast in the afternoon.

    High: 73 °F

    Mostly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 63.

    Low: 63 °F

    Partly Cloudy

  • Tuesday

    Tuesday: A 30 percent chance of showers after 2pm. Partly sunny, with a high near 78.

    High: 78 °F

    Mostly Sunny
    then Chance
    Showers

  • Tuesday Night

    Tuesday Night: A chance of showers before 8pm, then a chance of showers and thunderstorms between 8pm and 2am, then a chance of showers after 2am. Mostly cloudy, with a low around 65. Chance of precipitation is 50%.

    Low: 65 °F

    Chance
    T-storms

  • Wednesday

    Wednesday: A 30 percent chance of showers after 2pm. Partly sunny, with a high near 76.

    High: 76 °F

    Partly Sunny
    then Chance
    Showers

Detailed Forecast

This Afternoon
Sunny, with a high near 71. East wind around 10 mph.
Tonight
Partly cloudy, with a low around 55. Southeast wind around 7 mph.
Sunday
Mostly sunny, with a high near 69. East wind around 10 mph.
Sunday Night
Partly cloudy, with a low around 54. East wind 6 to 8 mph.
Monday
Mostly sunny, with a high near 73. Northeast wind around 6 mph becoming southeast in the afternoon.
Monday Night
Partly cloudy, with a low around 63.
Tuesday
A 30 percent chance of showers after 2pm. Partly sunny, with a high near 78.
Tuesday Night
A chance of showers before 8pm, then a chance of showers and thunderstorms between 8pm and 2am, then a chance of showers after 2am. Mostly cloudy, with a low around 65. Chance of precipitation is 50%.
Wednesday
A 30 percent chance of showers after 2pm. Partly sunny, with a high near 76.
Wednesday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 61.
Thursday
Partly sunny, with a high near 72.
Thursday Night
Mostly cloudy, with a low around 60.
Friday
Partly sunny, with a high near 73.
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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:
9:43 am EDT Sep 20, 2025
Forecast Valid:
1pm EDT Sep 20, 2025-6pm EDT Sep 26, 2025
 
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