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.

Overcast

47°F

8°C

Humidity 83%
Wind Speed SW 15 G 25 mph
Barometer 30.03 in (1016.8 mb)
Dewpoint 42°F (6°C)
Visibility 10.00 mi
Wind Chill41°F (5°C)
Last update 26 Mar 4:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: A 20 percent chance of rain. Cloudy, with a steady temperature around 46. South wind around 14 mph.

    Low: 46 °F

    Slight Chance
    Rain

  • Thursday

    Thursday: Cloudy, then gradually becoming mostly sunny, with a high near 61. Southwest wind around 14 mph.

    High: 61 °F

    Decreasing
    Clouds

  • Thursday Night

    Thursday Night: Showers, mainly after 11pm. Low around 44. South wind 10 to 18 mph becoming west after midnight. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 44 °F

    Showers

  • Friday

    Friday: Showers likely, mainly before 8am. Cloudy, with a steady temperature around 47. North wind 9 to 11 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

    High: 47 °F

    Showers
    Likely

  • Friday Night

    Friday Night: A slight chance of rain before 11pm, then a slight chance of rain and snow between 11pm and 2am, then a chance of snow after 2am. Mostly cloudy, with a low around 30. Northeast wind 3 to 7 mph. Chance of precipitation is 30%.

    Low: 30 °F

    Chance
    Rain/Snow

  • Saturday

    Saturday: A 30 percent chance of snow before 8am. Mostly sunny, with a high near 41.

    High: 41 °F

    Chance Snow
    then Mostly
    Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 29.

    Low: 29 °F

    Partly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 46.

    High: 46 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Mostly cloudy, with a low around 37.

    Low: 37 °F

    Mostly Cloudy

Detailed Forecast

Overnight
A 20 percent chance of rain. Cloudy, with a steady temperature around 46. South wind around 14 mph.
Thursday
Cloudy, then gradually becoming mostly sunny, with a high near 61. Southwest wind around 14 mph.
Thursday Night
Showers, mainly after 11pm. Low around 44. South wind 10 to 18 mph becoming west after midnight. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Friday
Showers likely, mainly before 8am. Cloudy, with a steady temperature around 47. North wind 9 to 11 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.
Friday Night
A slight chance of rain before 11pm, then a slight chance of rain and snow between 11pm and 2am, then a chance of snow after 2am. Mostly cloudy, with a low around 30. Northeast wind 3 to 7 mph. Chance of precipitation is 30%.
Saturday
A 30 percent chance of snow before 8am. Mostly sunny, with a high near 41.
Saturday Night
Partly cloudy, with a low around 29.
Sunday
Mostly sunny, with a high near 46.
Sunday Night
Mostly cloudy, with a low around 37.
Monday
Mostly cloudy, with a high near 54.
Monday Night
A 30 percent chance of rain. Mostly cloudy, with a low around 43.
Tuesday
A 40 percent chance of rain. Mostly cloudy, with a high near 53.
Tuesday Night
A 50 percent chance of rain. Mostly cloudy, with a low around 40.
Wednesday
A 40 percent chance of rain. Mostly cloudy, with a high near 52.
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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:
5:14 am EDT Mar 26, 2026
Forecast Valid:
5am EDT Mar 26, 2026-6pm EDT Apr 1, 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