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

56°F

13°C

Humidity 81%
Wind Speed SW 6 mph
Barometer 29.74 in (1006.9 mb)
Dewpoint 50°F (10°C)
Visibility 10.00 mi
Last update 30 Apr 5:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: A 20 percent chance of showers before 8pm. Partly cloudy, with a low around 45. Northwest wind 3 to 7 mph.

    Low: 45 °F

    Slight Chance
    Showers then
    Partly Cloudy

  • Friday

    Friday: Sunny, with a high near 63. West wind around 8 mph.

    High: 63 °F

    Sunny

  • Friday Night

    Friday Night: A 30 percent chance of showers, mainly after 2am. Increasing clouds, with a low around 46. Southwest wind 5 to 7 mph.

    Low: 46 °F

    Chance
    Showers

  • Saturday

    Saturday: A 30 percent chance of showers, mainly after 2pm. Mostly cloudy, with a high near 58. West wind around 6 mph becoming south in the afternoon.

    High: 58 °F

    Chance
    Showers

  • Saturday Night

    Saturday Night: A 50 percent chance of showers. Mostly cloudy, with a low around 45. Light and variable wind becoming north around 6 mph after midnight.

    Low: 45 °F

    Chance
    Showers

  • Sunday

    Sunday: Partly sunny, with a high near 59.

    High: 59 °F

    Partly Sunny

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 44.

    Low: 44 °F

    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 63.

    High: 63 °F

    Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 52.

    Low: 52 °F

    Partly Cloudy

Detailed Forecast

Tonight
A 20 percent chance of showers before 8pm. Partly cloudy, with a low around 45. Northwest wind 3 to 7 mph.
Friday
Sunny, with a high near 63. West wind around 8 mph.
Friday Night
A 30 percent chance of showers, mainly after 2am. Increasing clouds, with a low around 46. Southwest wind 5 to 7 mph.
Saturday
A 30 percent chance of showers, mainly after 2pm. Mostly cloudy, with a high near 58. West wind around 6 mph becoming south in the afternoon.
Saturday Night
A 50 percent chance of showers. Mostly cloudy, with a low around 45. Light and variable wind becoming north around 6 mph after midnight.
Sunday
Partly sunny, with a high near 59.
Sunday Night
Mostly clear, with a low around 44.
Monday
Sunny, with a high near 63.
Monday Night
Partly cloudy, with a low around 52.
Tuesday
Mostly sunny, with a high near 68.
Tuesday Night
Partly cloudy, with a low around 54.
Wednesday
A 40 percent chance of showers. Partly sunny, with a high near 65.
Wednesday Night
Showers likely. Mostly cloudy, with a low around 52. Chance of precipitation is 60%.
Thursday
Showers likely. Mostly cloudy, with a high near 64. Chance of precipitation is 70%.
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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:
2:27 pm EDT Apr 30, 2026
Forecast Valid:
6pm EDT Apr 30, 2026-6pm EDT May 7, 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