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

63°F

17°C

Humidity 58%
Wind Speed S 8 mph
Barometer 29.98 in (1015.2 mb)
Dewpoint 48°F (9°C)
Visibility 10.00 mi
Last update 10 Mar 2:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Partly cloudy, with a low around 39. South wind 5 to 10 mph becoming light in the evening.

    Low: 39 °F

    Partly Cloudy

  • Wednesday

    Wednesday: A 30 percent chance of showers, mainly after 2pm. Partly sunny, with a high near 56. Light south wind increasing to 5 to 10 mph in the morning.

    High: 56 °F

    Chance
    Showers

  • Wednesday Night

    Wednesday Night: A chance of rain before 11pm, then a chance of rain and thunderstorms between 11pm and 2am, then a chance of rain after 2am. Mostly cloudy, with a low around 47. South wind around 11 mph, with gusts as high as 22 mph. Chance of precipitation is 40%.

    Low: 47 °F

    Chance Rain

  • Thursday

    Thursday: Rain likely before 5pm, then a chance of rain and snow. Mostly cloudy, with a temperature rising to near 49 by 10am, then falling to around 42 during the remainder of the day. Northwest wind 11 to 14 mph, with gusts as high as 24 mph. Chance of precipitation is 70%. Little or no snow accumulation expected.

    High: 49 °F⇓

    Rain Likely
    then
    Rain/Snow
    Likely

  • Thursday Night

    Thursday Night: A chance of rain and snow before 8pm. Partly cloudy, with a low around 30. Northwest wind 7 to 10 mph. Chance of precipitation is 30%.

    Low: 30 °F

    Chance
    Rain/Snow
    then Mostly
    Clear

  • Friday

    Friday: Partly sunny, with a high near 44.

    High: 44 °F

    Partly Sunny

  • Friday Night

    Friday Night: Mostly cloudy, then gradually becoming mostly clear, with a low around 35.

    Low: 35 °F

    Decreasing
    Clouds

  • Saturday

    Saturday: Sunny, with a high near 47.

    High: 47 °F

    Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 32.

    Low: 32 °F

    Partly Cloudy

Detailed Forecast

Tonight
Partly cloudy, with a low around 39. South wind 5 to 10 mph becoming light in the evening.
Wednesday
A 30 percent chance of showers, mainly after 2pm. Partly sunny, with a high near 56. Light south wind increasing to 5 to 10 mph in the morning.
Wednesday Night
A chance of rain before 11pm, then a chance of rain and thunderstorms between 11pm and 2am, then a chance of rain after 2am. Mostly cloudy, with a low around 47. South wind around 11 mph, with gusts as high as 22 mph. Chance of precipitation is 40%.
Thursday
Rain likely before 5pm, then a chance of rain and snow. Mostly cloudy, with a temperature rising to near 49 by 10am, then falling to around 42 during the remainder of the day. Northwest wind 11 to 14 mph, with gusts as high as 24 mph. Chance of precipitation is 70%. Little or no snow accumulation expected.
Thursday Night
A chance of rain and snow before 8pm. Partly cloudy, with a low around 30. Northwest wind 7 to 10 mph. Chance of precipitation is 30%.
Friday
Partly sunny, with a high near 44.
Friday Night
Mostly cloudy, then gradually becoming mostly clear, with a low around 35.
Saturday
Sunny, with a high near 47.
Saturday Night
Partly cloudy, with a low around 32.
Sunday
Mostly cloudy, with a high near 50.
Sunday Night
Rain. Low around 43. Chance of precipitation is 80%.
Monday
Rain. High near 52. Chance of precipitation is 90%.
Monday Night
Rain and snow likely. Mostly cloudy, with a low around 27. Chance of precipitation is 60%.
Tuesday
A 30 percent chance of snow. Mostly sunny, with a high near 35.
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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:
1:57 pm EDT Mar 10, 2026
Forecast Valid:
3pm EDT Mar 10, 2026-6pm EDT Mar 17, 2026
 
Forecast Discussion
 
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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