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.

Fog/Mist

40°F

4°C

Humidity 97%
Wind Speed E 3 mph
Barometer 30.35 in (1027.9 mb)
Dewpoint 39°F (4°C)
Visibility 2.00 mi
Last update 3 Apr 4:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Patchy fog before 11am. Otherwise, cloudy, then gradually becoming mostly sunny, with a high near 60. Calm wind becoming southwest 5 to 8 mph in the afternoon.

    High: 60 °F

    Patchy Fog
    then Partly
    Sunny

  • Tonight

    Tonight: Patchy fog after 2am. Otherwise, mostly cloudy, with a low around 50. Southwest wind 7 to 10 mph.

    Low: 50 °F

    Mostly Cloudy
    then Patchy
    Fog

  • Saturday

    Saturday: A 20 percent chance of showers after 2pm. Patchy fog before 8am. Otherwise, partly sunny, with a high near 64. Light and variable wind becoming east 5 to 8 mph in the afternoon.

    High: 64 °F

    Patchy Fog
    then Slight
    Chance
    Showers

  • Saturday Night

    Saturday Night: A 50 percent chance of showers, mainly after 8pm. Mostly cloudy, with a low around 42. East wind 7 to 11 mph, with gusts as high as 21 mph.

    Low: 42 °F

    Chance
    Showers

  • Sunday

    Sunday: Showers. High near 60. South wind 10 to 14 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

    High: 60 °F

    Showers

  • Sunday Night

    Sunday Night: Cloudy, then gradually becoming partly cloudy, with a low around 39.

    Low: 39 °F

    Decreasing
    Clouds

  • Monday

    Monday: Mostly sunny, with a high near 52.

    High: 52 °F

    Mostly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 38.

    Low: 38 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Partly sunny, with a high near 50.

    High: 50 °F

    Partly Sunny

Detailed Forecast

Today
Patchy fog before 11am. Otherwise, cloudy, then gradually becoming mostly sunny, with a high near 60. Calm wind becoming southwest 5 to 8 mph in the afternoon.
Tonight
Patchy fog after 2am. Otherwise, mostly cloudy, with a low around 50. Southwest wind 7 to 10 mph.
Saturday
A 20 percent chance of showers after 2pm. Patchy fog before 8am. Otherwise, partly sunny, with a high near 64. Light and variable wind becoming east 5 to 8 mph in the afternoon.
Saturday Night
A 50 percent chance of showers, mainly after 8pm. Mostly cloudy, with a low around 42. East wind 7 to 11 mph, with gusts as high as 21 mph.
Sunday
Showers. High near 60. South wind 10 to 14 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Sunday Night
Cloudy, then gradually becoming partly cloudy, with a low around 39.
Monday
Mostly sunny, with a high near 52.
Monday Night
Partly cloudy, with a low around 38.
Tuesday
Partly sunny, with a high near 50.
Tuesday Night
Mostly clear, with a low around 31.
Wednesday
Sunny, with a high near 48.
Wednesday Night
Mostly clear, with a low around 36.
Thursday
Sunny, with a high near 55.
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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:
2:20 am EDT Apr 3, 2026
Forecast Valid:
5am EDT Apr 3, 2026-6pm EDT Apr 9, 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