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 68%
Wind Speed NE 7 mph
Barometer 30.25 in (1024.3 mb)
Dewpoint 34°F (1°C)
Visibility 10.00 mi
Wind Chill40°F (4°C)
Last update 4 Mar 12:56 pm EST
Extended Forecast for

Port Jefferson NY

  • This Afternoon

    This Afternoon: Mostly sunny, with a high near 40. Calm wind.

    High: 40 °F

    Mostly Sunny

  • Tonight

    Tonight: A 30 percent chance of rain after 4am. Patchy fog after 10pm. Otherwise, increasing clouds, with a low around 32. Calm wind.

    Low: 32 °F

    Patchy Fog
    then Chance
    Rain and
    Patchy Fog

  • Thursday

    Thursday: Rain, mainly after 7am. Patchy fog before 1pm. High near 38. Light northeast wind becoming east 6 to 11 mph in the morning. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

    High: 38 °F

    Rain and
    Patchy Fog

  • Thursday Night

    Thursday Night: Rain. Steady temperature around 38. Breezy, with a northeast wind 16 to 20 mph. Chance of precipitation is 100%. New precipitation amounts between a half and three quarters of an inch possible.

    Low: 38 °F

    Rain and
    Breezy

  • Friday

    Friday: A 30 percent chance of rain before 1pm. Cloudy, with a high near 40. Northeast wind 9 to 16 mph.

    High: 40 °F

    Chance Rain

  • Friday Night

    Friday Night: Cloudy, with a low around 36.

    Low: 36 °F

    Cloudy

  • Saturday

    Saturday: Cloudy, with a high near 48.

    High: 48 °F

    Cloudy

  • Saturday Night

    Saturday Night: Showers likely, mainly before 1am. Cloudy, with a low around 43. Chance of precipitation is 60%.

    Low: 43 °F

    Showers
    Likely

  • Sunday

    Sunday: Partly sunny, with a high near 50.

    High: 50 °F

    Partly Sunny

Detailed Forecast

This Afternoon
Mostly sunny, with a high near 40. Calm wind.
Tonight
A 30 percent chance of rain after 4am. Patchy fog after 10pm. Otherwise, increasing clouds, with a low around 32. Calm wind.
Thursday
Rain, mainly after 7am. Patchy fog before 1pm. High near 38. Light northeast wind becoming east 6 to 11 mph in the morning. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Thursday Night
Rain. Steady temperature around 38. Breezy, with a northeast wind 16 to 20 mph. Chance of precipitation is 100%. New precipitation amounts between a half and three quarters of an inch possible.
Friday
A 30 percent chance of rain before 1pm. Cloudy, with a high near 40. Northeast wind 9 to 16 mph.
Friday Night
Cloudy, with a low around 36.
Saturday
Cloudy, with a high near 48.
Saturday Night
Showers likely, mainly before 1am. Cloudy, with a low around 43. Chance of precipitation is 60%.
Sunday
Partly sunny, with a high near 50.
Sunday Night
Partly cloudy, with a low around 42.
Monday
Mostly sunny, with a high near 50.
Monday Night
Partly cloudy, with a low around 44.
Tuesday
Mostly sunny, with a high near 55.
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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:
1:01 pm EST Mar 4, 2026
Forecast Valid:
1pm EST Mar 4, 2026-6pm EDT Mar 10, 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