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

54°F

12°C

Humidity 80%
Wind Speed SW 13 mph
Barometer 30.17 in (1021.8 mb)
Dewpoint 48°F (9°C)
Visibility 10.00 mi
Wind Chill50°F (10°C)
Last update 3 Apr 3:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Patchy fog before 11pm, then patchy fog after 2am. Otherwise, mostly cloudy, with a steady temperature around 53. Southwest wind 10 to 14 mph.

    Low: 53 °F

    Patchy Fog

  • Saturday

    Saturday: A 20 percent chance of showers after 2pm. Patchy fog before 11am. Otherwise, partly sunny, with a steady temperature around 54. Northwest wind 6 to 10 mph becoming east in the afternoon.

    High: 54 °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 43. Breezy, with an east wind 11 to 20 mph.

    Low: 43 °F

    Chance
    Showers and
    Breezy

  • Sunday

    Sunday: Showers before 11am, then showers and possibly a thunderstorm between 11am and 2pm, then showers after 2pm. High near 58. Southwest wind 15 to 18 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

    High: 58 °F

    Showers

  • Sunday Night

    Sunday Night: Cloudy during the early evening, then gradual clearing, with a low around 42. Northwest wind 14 to 16 mph.

    Low: 42 °F

    Gradual
    Clearing

  • Monday

    Monday: Sunny, with a high near 51.

    High: 51 °F

    Sunny

  • Monday Night

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

    Low: 40 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 48.

    High: 48 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 33.

    Low: 33 °F

    Mostly Clear

Detailed Forecast

Tonight
Patchy fog before 11pm, then patchy fog after 2am. Otherwise, mostly cloudy, with a steady temperature around 53. Southwest wind 10 to 14 mph.
Saturday
A 20 percent chance of showers after 2pm. Patchy fog before 11am. Otherwise, partly sunny, with a steady temperature around 54. Northwest wind 6 to 10 mph becoming east in the afternoon.
Saturday Night
A 40 percent chance of showers, mainly after 8pm. Cloudy, with a low around 43. Breezy, with an east wind 11 to 20 mph.
Sunday
Showers before 11am, then showers and possibly a thunderstorm between 11am and 2pm, then showers after 2pm. High near 58. Southwest wind 15 to 18 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 42. Northwest wind 14 to 16 mph.
Monday
Sunny, with a high near 51.
Monday Night
Partly cloudy, with a low around 40.
Tuesday
Mostly sunny, with a high near 48.
Tuesday Night
Mostly clear, with a low around 33.
Wednesday
Sunny, with a high near 46.
Wednesday Night
Mostly clear, with a low around 38.
Thursday
Mostly sunny, with a high near 53.
Thursday Night
Partly cloudy, with a low around 45.
Friday
Mostly sunny, with a high near 58.
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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:
2:23 pm EDT Apr 3, 2026
Forecast Valid:
4pm EDT Apr 3, 2026-6pm EDT Apr 10, 2026
 
Forecast Discussion
 
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Additional Resources

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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