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

38°F

3°C

Humidity 65%
Wind Speed S 9 mph
Barometer 29.87 in (1011.4 mb)
Dewpoint 27°F (-3°C)
Visibility 10.00 mi
Wind Chill32°F (0°C)
Last update 26 Feb 1:56 pm EST
Extended Forecast for

Port Jefferson NY

  • This Afternoon

    This Afternoon: A slight chance of rain and snow showers after 4pm. Mostly cloudy, with a high near 36. Southwest wind around 6 mph. Chance of precipitation is 20%.

    High: 36 °F

    Slight Chance
    Rain/Snow

  • Tonight

    Tonight: Cloudy during the early evening, then gradual clearing, with a low around 27. Light and variable wind becoming north around 6 mph in the evening.

    Low: 27 °F

    Gradual
    Clearing

  • Friday

    Friday: Sunny, with a high near 37. Wind chill values between 25 and 30. Calm wind becoming southwest around 6 mph in the afternoon.

    High: 37 °F

    Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 32. South wind around 6 mph.

    Low: 32 °F

    Mostly Clear

  • Saturday

    Saturday: Mostly sunny, with a high near 42. South wind around 7 mph.

    High: 42 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 31.

    Low: 31 °F

    Partly Cloudy

  • Sunday

    Sunday: Partly sunny, with a high near 35.

    High: 35 °F

    Partly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 20.

    Low: 20 °F

    Partly Cloudy

  • Monday

    Monday: A 30 percent chance of snow after 1pm. Partly sunny, with a high near 28.

    High: 28 °F

    Mostly Sunny
    then Chance
    Snow

Detailed Forecast

This Afternoon
A slight chance of rain and snow showers after 4pm. Mostly cloudy, with a high near 36. Southwest wind around 6 mph. Chance of precipitation is 20%.
Tonight
Cloudy during the early evening, then gradual clearing, with a low around 27. Light and variable wind becoming north around 6 mph in the evening.
Friday
Sunny, with a high near 37. Wind chill values between 25 and 30. Calm wind becoming southwest around 6 mph in the afternoon.
Friday Night
Mostly clear, with a low around 32. South wind around 6 mph.
Saturday
Mostly sunny, with a high near 42. South wind around 7 mph.
Saturday Night
Partly cloudy, with a low around 31.
Sunday
Partly sunny, with a high near 35.
Sunday Night
Partly cloudy, with a low around 20.
Monday
A 30 percent chance of snow after 1pm. Partly sunny, with a high near 28.
Monday Night
Partly cloudy, with a low around 23.
Tuesday
Partly sunny, with a high near 35.
Tuesday Night
A 50 percent chance of rain. Mostly cloudy, with a low around 32.
Wednesday
A 40 percent chance of rain. Partly sunny, with a high near 42.
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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:
12:59 pm EST Feb 26, 2026
Forecast Valid:
2pm EST Feb 26, 2026-6pm EST Mar 4, 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