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

77°F

25°C

Humidity 48%
Wind Speed E 6 mph
Barometer 30.17 in (1021.5 mb)
Dewpoint 56°F (13°C)
Visibility 10.00 mi
Heat Index79°F (26°C)
Last update 15 Aug 10:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Sunny, with a high near 81. North wind 5 to 7 mph.

    High: 81 °F

    Sunny

  • Tonight

    Tonight: Mostly clear, with a low around 66. Light and variable wind.

    Low: 66 °F

    Mostly Clear

  • Sunday

    Sunday: A 30 percent chance of showers after 5pm. Mostly sunny, with a high near 81. Light and variable wind becoming south 6 to 11 mph in the morning.

    High: 81 °F

    Sunny then
    Chance
    Showers

  • Sunday Night

    Sunday Night: Showers likely before 11pm, then showers likely and possibly a thunderstorm between 11pm and 2am, then showers after 2am. Low around 68. South wind 11 to 14 mph. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.

    Low: 68 °F

    Showers

  • Monday

    Monday: Showers, mainly before 8am. High near 84. South wind 8 to 13 mph becoming north in the morning. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    High: 84 °F

    Showers then
    Slight Chance
    Showers

  • Monday Night

    Monday Night: Partly cloudy, with a low around 67.

    Low: 67 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Sunny, with a high near 83.

    High: 83 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 68.

    Low: 68 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 84.

    High: 84 °F

    Sunny

Detailed Forecast

Today
Sunny, with a high near 81. North wind 5 to 7 mph.
Tonight
Mostly clear, with a low around 66. Light and variable wind.
Sunday
A 30 percent chance of showers after 5pm. Mostly sunny, with a high near 81. Light and variable wind becoming south 6 to 11 mph in the morning.
Sunday Night
Showers likely before 11pm, then showers likely and possibly a thunderstorm between 11pm and 2am, then showers after 2am. Low around 68. South wind 11 to 14 mph. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.
Monday
Showers, mainly before 8am. High near 84. South wind 8 to 13 mph becoming north in the morning. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Monday Night
Partly cloudy, with a low around 67.
Tuesday
Sunny, with a high near 83.
Tuesday Night
Mostly clear, with a low around 68.
Wednesday
Sunny, with a high near 84.
Wednesday Night
A 30 percent chance of showers after 2am. Partly cloudy, with a low around 70.
Thursday
A 40 percent chance of showers. Partly sunny, with a high near 83.
Thursday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 65.
Friday
Mostly sunny, with a high near 79.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.93°N 73.06°W (Elev. 161 ft)
Last Update:
2:20 am EDT Aug 15, 2026
Forecast Valid:
11am EDT Aug 15, 2026-6pm EDT Aug 21, 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