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.

Partly Cloudy

45°F

7°C

Humidity 58%
Wind Speed S 13 mph
Barometer 30.30 in (1026.0 mb)
Dewpoint 31°F (-1°C)
Visibility 10.00 mi
Wind Chill39°F (4°C)
Last update 25 Mar 3:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly cloudy, with a low around 41. South wind 11 to 14 mph.

    Low: 41 °F

    Mostly Cloudy

  • Thursday

    Thursday: A slight chance of showers before 11am, then a slight chance of showers after 5pm. Cloudy, then gradually becoming mostly sunny, with a high near 56. Southwest wind around 16 mph. Chance of precipitation is 20%.

    High: 56 °F

    Slight Chance
    Showers then
    Mostly Sunny

  • Thursday Night

    Thursday Night: Showers, mainly after 2am. Low around 46. South wind 13 to 18 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 46 °F

    Chance
    Showers then
    Showers

  • Friday

    Friday: Showers, mainly before 2pm. High near 50. North wind 11 to 14 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    High: 50 °F

    Showers

  • Friday Night

    Friday Night: A slight chance of rain showers, mixing with snow after 11pm, then gradually ending. Mostly cloudy, with a low around 31. North wind 10 to 13 mph. Chance of precipitation is 20%.

    Low: 31 °F

    Slight Chance
    Rain/Snow

  • Saturday

    Saturday: Mostly sunny, with a high near 40.

    High: 40 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 31.

    Low: 31 °F

    Partly Cloudy

  • Sunday

    Sunday: Sunny, with a high near 45.

    High: 45 °F

    Sunny

  • Sunday Night

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

    Low: 39 °F

    Partly Cloudy

Detailed Forecast

Tonight
Mostly cloudy, with a low around 41. South wind 11 to 14 mph.
Thursday
A slight chance of showers before 11am, then a slight chance of showers after 5pm. Cloudy, then gradually becoming mostly sunny, with a high near 56. Southwest wind around 16 mph. Chance of precipitation is 20%.
Thursday Night
Showers, mainly after 2am. Low around 46. South wind 13 to 18 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Friday
Showers, mainly before 2pm. High near 50. North wind 11 to 14 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Friday Night
A slight chance of rain showers, mixing with snow after 11pm, then gradually ending. Mostly cloudy, with a low around 31. North wind 10 to 13 mph. Chance of precipitation is 20%.
Saturday
Mostly sunny, with a high near 40.
Saturday Night
Partly cloudy, with a low around 31.
Sunday
Sunny, with a high near 45.
Sunday Night
Partly cloudy, with a low around 39.
Monday
Mostly cloudy, with a high near 50.
Monday Night
Mostly cloudy, with a low around 44.
Tuesday
Mostly cloudy, with a high near 50.
Tuesday Night
A 40 percent chance of rain. Mostly cloudy, with a low around 41.
Wednesday
A 30 percent chance of rain. Mostly cloudy, with a high near 49.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
2:46 pm EDT Mar 25, 2026
Forecast Valid:
4pm EDT Mar 25, 2026-6pm EDT Apr 1, 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