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

40°F

4°C

Humidity 25%
Wind Speed N 9 mph
Barometer 30.40 in (1029.4 mb)
Dewpoint 7°F (-14°C)
Visibility 10.00 mi
Wind Chill34°F (1°C)
Last update 28 Mar 4:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly clear, with a low around 32. Northwest wind 9 to 14 mph becoming light after midnight. Winds could gust as high as 25 mph.

    Low: 32 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny, with a high near 46. Southwest wind 6 to 15 mph.

    High: 46 °F

    Sunny

  • Sunday Night

    Sunday Night: Increasing clouds, with a low around 42. Breezy, with a southwest wind 15 to 20 mph.

    Low: 42 °F

    Increasing
    Clouds and
    Breezy then
    Mostly Cloudy

  • Monday

    Monday: Partly sunny, with a high near 55. Southwest wind around 16 mph.

    High: 55 °F

    Partly Sunny

  • Monday Night

    Monday Night: A 30 percent chance of showers after 2am. Mostly cloudy, with a low around 48. Southwest wind 10 to 14 mph.

    Low: 48 °F

    Mostly Cloudy
    then Chance
    Showers

  • Tuesday

    Tuesday: A 30 percent chance of showers before 8am. Partly sunny, with a high near 60.

    High: 60 °F

    Chance
    Showers then
    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 52. Breezy.

    Low: 52 °F

    Partly Cloudy
    and Breezy

  • Wednesday

    Wednesday: A 50 percent chance of rain after 2pm. Partly sunny, with a high near 62.

    High: 62 °F

    Partly Sunny
    then Chance
    Rain

  • Wednesday Night

    Wednesday Night: Rain likely, mainly after 8pm. Mostly cloudy, with a low around 41. Chance of precipitation is 70%.

    Low: 41 °F

    Rain Likely

Detailed Forecast

Tonight
Mostly clear, with a low around 32. Northwest wind 9 to 14 mph becoming light after midnight. Winds could gust as high as 25 mph.
Sunday
Sunny, with a high near 46. Southwest wind 6 to 15 mph.
Sunday Night
Increasing clouds, with a low around 42. Breezy, with a southwest wind 15 to 20 mph.
Monday
Partly sunny, with a high near 55. Southwest wind around 16 mph.
Monday Night
A 30 percent chance of showers after 2am. Mostly cloudy, with a low around 48. Southwest wind 10 to 14 mph.
Tuesday
A 30 percent chance of showers before 8am. Partly sunny, with a high near 60.
Tuesday Night
Partly cloudy, with a low around 52. Breezy.
Wednesday
A 50 percent chance of rain after 2pm. Partly sunny, with a high near 62.
Wednesday Night
Rain likely, mainly after 8pm. Mostly cloudy, with a low around 41. Chance of precipitation is 70%.
Thursday
A 50 percent chance of rain. Mostly cloudy, with a high near 44.
Thursday Night
Rain and snow likely. Cloudy, with a low around 37. Chance of precipitation is 60%.
Friday
Rain and snow likely. Cloudy, with a high near 44. Breezy. Chance of precipitation is 60%.
Friday Night
Rain likely. Cloudy, with a low around 38. Chance of precipitation is 60%.
Saturday
A 40 percent chance of rain. Mostly cloudy, with a high near 48.
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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:
2:35 pm EDT Mar 28, 2026
Forecast Valid:
5pm EDT Mar 28, 2026-6pm EDT Apr 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