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.

Fog/Mist

33°F

1°C

Humidity 96%
Wind Speed Calm
Barometer 30.03 in (1016.9 mb)
Dewpoint 32°F (0°C)
Visibility 4.00 mi
Last update 28 Feb 10:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Areas of fog before 2am. Otherwise, cloudy, then gradually becoming partly cloudy, with a low around 27. Calm wind becoming north 5 to 7 mph after midnight.

    Low: 27 °F

    Areas Fog

  • Sunday

    Sunday: Snow likely, mainly before 1pm. Cloudy, with a high near 34. Wind chill values between 15 and 25. North wind 8 to 13 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible.

    High: 34 °F

    Snow Likely

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 15. Wind chill values between zero and 10. North wind 14 to 16 mph.

    Low: 15 °F

    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 28. Wind chill values between zero and 10. North wind 5 to 13 mph becoming west in the afternoon.

    High: 28 °F

    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 19. South wind 3 to 6 mph.

    Low: 19 °F

    Mostly Clear

  • Tuesday

    Tuesday: A chance of rain and snow before 1pm, then rain likely. Mostly cloudy, with a high near 40. Chance of precipitation is 70%. Little or no snow accumulation expected.

    High: 40 °F

    Chance
    Rain/Snow
    then
    Rain/Snow
    Likely

  • Tuesday Night

    Tuesday Night: Rain. Low around 38. Chance of precipitation is 90%.

    Low: 38 °F

    Rain

  • Wednesday

    Wednesday: Mostly cloudy, with a high near 44.

    High: 44 °F

    Mostly Cloudy

  • Wednesday Night

    Wednesday Night: A 40 percent chance of rain. Cloudy, with a low around 37.

    Low: 37 °F

    Chance Rain

Detailed Forecast

Tonight
Areas of fog before 2am. Otherwise, cloudy, then gradually becoming partly cloudy, with a low around 27. Calm wind becoming north 5 to 7 mph after midnight.
Sunday
Snow likely, mainly before 1pm. Cloudy, with a high near 34. Wind chill values between 15 and 25. North wind 8 to 13 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible.
Sunday Night
Mostly clear, with a low around 15. Wind chill values between zero and 10. North wind 14 to 16 mph.
Monday
Sunny, with a high near 28. Wind chill values between zero and 10. North wind 5 to 13 mph becoming west in the afternoon.
Monday Night
Mostly clear, with a low around 19. South wind 3 to 6 mph.
Tuesday
A chance of rain and snow before 1pm, then rain likely. Mostly cloudy, with a high near 40. Chance of precipitation is 70%. Little or no snow accumulation expected.
Tuesday Night
Rain. Low around 38. Chance of precipitation is 90%.
Wednesday
Mostly cloudy, with a high near 44.
Wednesday Night
A 40 percent chance of rain. Cloudy, with a low around 37.
Thursday
A 40 percent chance of rain. Cloudy, with a high near 48.
Thursday Night
A 50 percent chance of rain. Cloudy, with a low around 40.
Friday
A 40 percent chance of rain. Cloudy, with a high near 45.
Friday Night
A 30 percent chance of rain. Cloudy, with a low around 40.
Saturday
Mostly cloudy, with a high near 50.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
11:34 pm EST Feb 28, 2026
Forecast Valid:
11pm EST Feb 28, 2026-6pm EST Mar 7, 2026
 
Forecast Discussion
 
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Additional Resources

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Hourly Weather Forecast

National Digital Forecast Database

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation