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 77%
Wind Speed SW 9 G 21 mph
Barometer 30.19 in (1022.3 mb)
Dewpoint 49°F (9°C)
Visibility 10.00 mi
Last update 3 Apr 2:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Patchy fog after 8pm. Otherwise, mostly cloudy, with a low around 51. Southwest wind 7 to 10 mph.

    Low: 51 °F

    Patchy Fog

  • Saturday

    Saturday: A 20 percent chance of showers after 2pm. Patchy fog before 11am. Otherwise, partly sunny, with a high near 61. Light and variable wind becoming east 5 to 10 mph in the morning.

    High: 61 °F

    Patchy Fog
    then Slight
    Chance
    Showers

  • Saturday Night

    Saturday Night: A 40 percent chance of showers, mainly after 8pm. Cloudy, with a low around 41. East wind 7 to 13 mph.

    Low: 41 °F

    Chance
    Showers

  • Sunday

    Sunday: Showers before 11am, then showers and possibly a thunderstorm between 11am and 2pm, then showers after 2pm. High near 59. South wind 10 to 15 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

    High: 59 °F

    Showers

  • Sunday Night

    Sunday Night: Cloudy during the early evening, then gradual clearing, with a low around 41. Northwest wind around 9 mph.

    Low: 41 °F

    Gradual
    Clearing

  • Monday

    Monday: Sunny, with a high near 53.

    High: 53 °F

    Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 39.

    Low: 39 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 50.

    High: 50 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 31.

    Low: 31 °F

    Mostly Clear

Detailed Forecast

Tonight
Patchy fog after 8pm. Otherwise, mostly cloudy, with a low around 51. Southwest wind 7 to 10 mph.
Saturday
A 20 percent chance of showers after 2pm. Patchy fog before 11am. Otherwise, partly sunny, with a high near 61. Light and variable wind becoming east 5 to 10 mph in the morning.
Saturday Night
A 40 percent chance of showers, mainly after 8pm. Cloudy, with a low around 41. East wind 7 to 13 mph.
Sunday
Showers before 11am, then showers and possibly a thunderstorm between 11am and 2pm, then showers after 2pm. High near 59. South wind 10 to 15 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.
Sunday Night
Cloudy during the early evening, then gradual clearing, with a low around 41. Northwest wind around 9 mph.
Monday
Sunny, with a high near 53.
Monday Night
Partly cloudy, with a low around 39.
Tuesday
Mostly sunny, with a high near 50.
Tuesday Night
Mostly clear, with a low around 31.
Wednesday
Sunny, with a high near 47.
Wednesday Night
Mostly clear, with a low around 36.
Thursday
Mostly sunny, with a high near 55.
Thursday Night
Partly cloudy, with a low around 43.
Friday
Mostly sunny, with a high near 61.
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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:
2:23 pm EDT Apr 3, 2026
Forecast Valid:
3pm EDT Apr 3, 2026-6pm EDT Apr 10, 2026
 
Forecast Discussion
 
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Additional Resources

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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