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

44°F

7°C

Humidity 49%
Wind Speed S 17 G 22 mph
Barometer 29.93 in
Dewpoint 26°F (-3°C)
Visibility 10.00 mi
Wind Chill36°F (2°C)
Last update 13 Jan 2:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: A 20 percent chance of rain after 4am. Mostly cloudy, with a low around 41. Southwest wind 14 to 18 mph.

    Low: 41 °F

    Mostly Cloudy
    then Slight
    Chance Rain

  • Wednesday

    Wednesday: A slight chance of rain before 10am, then a slight chance of rain after 4pm. Cloudy, with a high near 46. Southwest wind 7 to 11 mph. Chance of precipitation is 20%.

    High: 46 °F

    Slight Chance
    Rain

  • Wednesday Night

    Wednesday Night: A 50 percent chance of rain, mainly after 1am. Cloudy, with a low around 31. South wind 6 to 10 mph.

    Low: 31 °F

    Slight Chance
    Rain then
    Chance Rain

  • Thursday

    Thursday: A slight chance of rain, mixing with snow after 10am, then gradually ending. Cloudy, then gradually becoming mostly sunny, with a temperature rising to near 35 by 10am, then falling to around 29 during the remainder of the day. Wind chill values between 15 and 25. Breezy, with a west wind 15 to 22 mph. Chance of precipitation is 20%.

    High: 35 °F⇓

    Slight Chance
    Rain/Snow and
    Breezy

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 21. Breezy, with a west wind 20 to 22 mph.

    Low: 21 °F

    Partly Cloudy
    and Breezy

  • Friday

    Friday: Mostly sunny, with a high near 35.

    High: 35 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Mostly cloudy, with a low around 32.

    Low: 32 °F

    Mostly Cloudy

  • Saturday

    Saturday: Partly sunny, with a high near 40.

    High: 40 °F

    Partly Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 29.

    Low: 29 °F

    Mostly Cloudy

Detailed Forecast

Tonight
A 20 percent chance of rain after 4am. Mostly cloudy, with a low around 41. Southwest wind 14 to 18 mph.
Wednesday
A slight chance of rain before 10am, then a slight chance of rain after 4pm. Cloudy, with a high near 46. Southwest wind 7 to 11 mph. Chance of precipitation is 20%.
Wednesday Night
A 50 percent chance of rain, mainly after 1am. Cloudy, with a low around 31. South wind 6 to 10 mph.
Thursday
A slight chance of rain, mixing with snow after 10am, then gradually ending. Cloudy, then gradually becoming mostly sunny, with a temperature rising to near 35 by 10am, then falling to around 29 during the remainder of the day. Wind chill values between 15 and 25. Breezy, with a west wind 15 to 22 mph. Chance of precipitation is 20%.
Thursday Night
Partly cloudy, with a low around 21. Breezy, with a west wind 20 to 22 mph.
Friday
Mostly sunny, with a high near 35.
Friday Night
Mostly cloudy, with a low around 32.
Saturday
Partly sunny, with a high near 40.
Saturday Night
Mostly cloudy, with a low around 29.
Sunday
Partly sunny, with a high near 33.
Sunday Night
Partly cloudy, with a low around 24.
M.L.King Day
Mostly sunny, with a high near 31.
Monday Night
Partly cloudy, with a low around 22. Breezy.
Tuesday
Mostly sunny, with a high near 27. Breezy.
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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:
12:35 pm EST Jan 13, 2026
Forecast Valid:
3pm EST Jan 13, 2026-6pm EST Jan 20, 2026
 
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Additional Resources

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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