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

52°F

11°C

Humidity 69%
Wind Speed SW 14 mph
Barometer 29.97 in (1014.9 mb)
Dewpoint 42°F (6°C)
Visibility 10.00 mi
Wind Chill47°F (8°C)
Last update 21 Nov 1:56 pm EST
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Showers likely, mainly after 4am. Cloudy, with a steady temperature around 47. Southwest wind 5 to 7 mph becoming northwest after midnight. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

    Low: 47 °F

    Cloudy then
    Showers
    Likely

  • Saturday

    Saturday: Showers likely before 10am, then a chance of rain between 10am and 1pm. Cloudy through mid morning, then gradual clearing, with a high near 49. North wind 6 to 9 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

    High: 49 °F

    Showers
    Likely then
    Chance Rain

  • Saturday Night

    Saturday Night: Areas of frost after 2am. Otherwise, partly cloudy, with a low around 35. North wind 6 to 10 mph.

    Low: 35 °F

    Mostly Clear
    then Areas
    Frost

  • Sunday

    Sunday: Areas of frost before 9am. Otherwise, mostly sunny, with a high near 49. Northwest wind 5 to 10 mph becoming southwest in the afternoon.

    High: 49 °F

    Areas Frost
    then Mostly
    Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 40. West wind around 11 mph.

    Low: 40 °F

    Partly Cloudy

  • Monday

    Monday: Sunny, with a high near 50.

    High: 50 °F

    Sunny

  • Monday Night

    Monday Night: Increasing clouds, with a low around 39.

    Low: 39 °F

    Increasing
    Clouds

  • Tuesday

    Tuesday: A 30 percent chance of rain after 1pm. Cloudy, with a high near 54.

    High: 54 °F

    Mostly Cloudy
    then Chance
    Rain

  • Tuesday Night

    Tuesday Night: Rain likely. Cloudy, with a low around 49. Chance of precipitation is 70%.

    Low: 49 °F

    Rain Likely

Detailed Forecast

Tonight
Showers likely, mainly after 4am. Cloudy, with a steady temperature around 47. Southwest wind 5 to 7 mph becoming northwest after midnight. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.
Saturday
Showers likely before 10am, then a chance of rain between 10am and 1pm. Cloudy through mid morning, then gradual clearing, with a high near 49. North wind 6 to 9 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.
Saturday Night
Areas of frost after 2am. Otherwise, partly cloudy, with a low around 35. North wind 6 to 10 mph.
Sunday
Areas of frost before 9am. Otherwise, mostly sunny, with a high near 49. Northwest wind 5 to 10 mph becoming southwest in the afternoon.
Sunday Night
Partly cloudy, with a low around 40. West wind around 11 mph.
Monday
Sunny, with a high near 50.
Monday Night
Increasing clouds, with a low around 39.
Tuesday
A 30 percent chance of rain after 1pm. Cloudy, with a high near 54.
Tuesday Night
Rain likely. Cloudy, with a low around 49. Chance of precipitation is 70%.
Wednesday
A 50 percent chance of rain. Mostly cloudy, with a high near 57.
Wednesday Night
A 40 percent chance of rain. Mostly cloudy, with a low around 42.
Thanksgiving Day
Mostly sunny, with a high near 50.
Thursday Night
Partly cloudy, with a low around 35.
Friday
Mostly sunny, with a high near 44.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
1:45 pm EST Nov 21, 2025
Forecast Valid:
3pm EST Nov 21, 2025-6pm EST Nov 28, 2025
 
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Additional Resources

Radar & Satellite Image

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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