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.

Fair

38°F

3°C

Humidity 68%
Wind Speed N 7 mph
Barometer 30.46 in (1031.6 mb)
Dewpoint 28°F (-2°C)
Visibility 10.00 mi
Wind Chill33°F (1°C)
Last update 12 Apr 4:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Increasing clouds, with a high near 55. North wind 5 to 8 mph becoming south in the afternoon.

    High: 55 °F

    Increasing
    Clouds

  • Tonight

    Tonight: Mostly cloudy, with a low around 44. South wind 6 to 9 mph.

    Low: 44 °F

    Mostly Cloudy

  • Monday

    Monday: A 20 percent chance of showers after 2pm. Mostly cloudy, with a high near 68. Southwest wind 10 to 14 mph, with gusts as high as 24 mph.

    High: 68 °F

    Mostly Cloudy
    then Slight
    Chance
    Showers

  • Monday Night

    Monday Night: Mostly cloudy, then gradually becoming mostly clear, with a low around 53. Southwest wind 6 to 13 mph.

    Low: 53 °F

    Decreasing
    Clouds

  • Tuesday

    Tuesday: Mostly sunny, with a high near 75. Southwest wind 5 to 10 mph.

    High: 75 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 57.

    Low: 57 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Mostly sunny, with a high near 81.

    High: 81 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: A chance of showers between 8pm and 2am. Mostly cloudy, with a low around 59. Chance of precipitation is 40%.

    Low: 59 °F

    Chance
    Showers

  • Thursday

    Thursday: Partly sunny, with a high near 79.

    High: 79 °F

    Partly Sunny

Detailed Forecast

Today
Increasing clouds, with a high near 55. North wind 5 to 8 mph becoming south in the afternoon.
Tonight
Mostly cloudy, with a low around 44. South wind 6 to 9 mph.
Monday
A 20 percent chance of showers after 2pm. Mostly cloudy, with a high near 68. Southwest wind 10 to 14 mph, with gusts as high as 24 mph.
Monday Night
Mostly cloudy, then gradually becoming mostly clear, with a low around 53. Southwest wind 6 to 13 mph.
Tuesday
Mostly sunny, with a high near 75. Southwest wind 5 to 10 mph.
Tuesday Night
Mostly cloudy, with a low around 57.
Wednesday
Mostly sunny, with a high near 81.
Wednesday Night
A chance of showers between 8pm and 2am. Mostly cloudy, with a low around 59. Chance of precipitation is 40%.
Thursday
Partly sunny, with a high near 79.
Thursday Night
Mostly cloudy, with a low around 57.
Friday
Mostly sunny, with a high near 71.
Friday Night
Partly cloudy, with a low around 52.
Saturday
Mostly sunny, with a high near 67.
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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:
4:15 am EDT Apr 12, 2026
Forecast Valid:
5am EDT Apr 12, 2026-6pm EDT Apr 18, 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