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.

Overcast

71°F

22°C

Humidity 84%
Wind Speed SW 10 G 21 mph
Barometer 29.96 in (1014.4 mb)
Dewpoint 66°F (19°C)
Visibility 10.00 mi
Last update 16 Aug 11:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Showers, with thunderstorms also possible after 2am. Low around 70. South wind 14 to 16 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 70 °F

    Showers

  • Monday

    Monday: Showers likely and possibly a thunderstorm before 11am, then a chance of showers between 11am and 2pm. Cloudy, then gradually becoming mostly sunny, with a high near 79. Southeast wind 6 to 11 mph becoming northwest in the afternoon. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

    High: 79 °F

    Showers
    Likely then
    Chance
    Showers

  • Monday Night

    Monday Night: A slight chance of showers between 8pm and 2am. Partly cloudy, with a low around 72. Light and variable wind becoming north 5 to 7 mph after midnight. Chance of precipitation is 20%.

    Low: 72 °F

    Slight Chance
    Showers

  • Tuesday

    Tuesday: Partly sunny, then gradually becoming sunny, with a high near 82. North wind 5 to 9 mph becoming light and variable in the afternoon.

    High: 82 °F

    Becoming
    Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 71. West wind 3 to 5 mph.

    Low: 71 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 84.

    High: 84 °F

    Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 70.

    Low: 70 °F

    Partly Cloudy

  • Thursday

    Thursday: A chance of showers, with thunderstorms also possible after 2pm. Partly sunny, with a high near 80. Chance of precipitation is 50%.

    High: 80 °F

    Chance
    Showers then
    Chance
    T-storms

  • Thursday Night

    Thursday Night: A chance of thunderstorms before 8pm. Mostly cloudy, with a low around 66. Chance of precipitation is 30%.

    Low: 66 °F

    Chance
    T-storms then
    Partly Cloudy

Detailed Forecast

Overnight
Showers, with thunderstorms also possible after 2am. Low around 70. South wind 14 to 16 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Monday
Showers likely and possibly a thunderstorm before 11am, then a chance of showers between 11am and 2pm. Cloudy, then gradually becoming mostly sunny, with a high near 79. Southeast wind 6 to 11 mph becoming northwest in the afternoon. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.
Monday Night
A slight chance of showers between 8pm and 2am. Partly cloudy, with a low around 72. Light and variable wind becoming north 5 to 7 mph after midnight. Chance of precipitation is 20%.
Tuesday
Partly sunny, then gradually becoming sunny, with a high near 82. North wind 5 to 9 mph becoming light and variable in the afternoon.
Tuesday Night
Mostly clear, with a low around 71. West wind 3 to 5 mph.
Wednesday
Sunny, with a high near 84.
Wednesday Night
Partly cloudy, with a low around 70.
Thursday
A chance of showers, with thunderstorms also possible after 2pm. Partly sunny, with a high near 80. Chance of precipitation is 50%.
Thursday Night
A chance of thunderstorms before 8pm. Mostly cloudy, with a low around 66. Chance of precipitation is 30%.
Friday
Mostly sunny, with a high near 78.
Friday Night
Mostly cloudy, with a low around 67.
Saturday
Partly sunny, with a high near 77.
Saturday Night
Mostly cloudy, with a low around 67.
Sunday
A 30 percent chance of showers. Partly sunny, with a high near 79.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
2:20 pm EDT Aug 16, 2026
Forecast Valid:
12am EDT Aug 17, 2026-6pm EDT Aug 23, 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