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

66°F

19°C

Humidity 56%
Wind Speed SE 8 mph
Barometer 30.21 in (1023.1 mb)
Dewpoint 50°F (10°C)
Visibility 10.00 mi
Last update 4 Apr 12:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • This Afternoon

    This Afternoon: Partly sunny, with a high near 51. East wind 11 to 14 mph.

    High: 51 °F

    Partly Sunny

  • Tonight

    Tonight: A 50 percent chance of rain, mainly after 11pm. Cloudy, with a low around 42. East wind 11 to 18 mph.

    Low: 42 °F

    Chance Rain

  • Sunday

    Sunday: Rain and possibly a thunderstorm. High near 56. South wind 14 to 18 mph. Chance of precipitation is 100%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    High: 56 °F

    Rain

  • Sunday Night

    Sunday Night: Rain likely before 8pm. Cloudy during the early evening, then gradual clearing, with a low around 41. Northwest wind 13 to 16 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

    Low: 41 °F

    Rain Likely
    then Partly
    Cloudy

  • Monday

    Monday: Sunny, with a high near 51. West wind 14 to 16 mph.

    High: 51 °F

    Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 40.

    Low: 40 °F

    Partly Cloudy

  • Tuesday

    Tuesday: A 30 percent chance of showers before 2pm. Mostly sunny, with a high near 48.

    High: 48 °F

    Chance
    Showers

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 32.

    Low: 32 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 45.

    High: 45 °F

    Sunny

Detailed Forecast

This Afternoon
Partly sunny, with a high near 51. East wind 11 to 14 mph.
Tonight
A 50 percent chance of rain, mainly after 11pm. Cloudy, with a low around 42. East wind 11 to 18 mph.
Sunday
Rain and possibly a thunderstorm. High near 56. South wind 14 to 18 mph. Chance of precipitation is 100%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Sunday Night
Rain likely before 8pm. Cloudy during the early evening, then gradual clearing, with a low around 41. Northwest wind 13 to 16 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.
Monday
Sunny, with a high near 51. West wind 14 to 16 mph.
Monday Night
Partly cloudy, with a low around 40.
Tuesday
A 30 percent chance of showers before 2pm. Mostly sunny, with a high near 48.
Tuesday Night
Mostly clear, with a low around 32.
Wednesday
Sunny, with a high near 45.
Wednesday Night
Mostly clear, with a low around 37.
Thursday
Sunny, with a high near 53.
Thursday Night
Mostly clear, with a low around 44.
Friday
Mostly sunny, with a high near 57.
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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:
10:06 am EDT Apr 4, 2026
Forecast Valid:
1pm EDT Apr 4, 2026-6pm EDT Apr 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