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

42°F

6°C

Humidity 85%
Wind Speed SE 13 G 22 mph
Barometer 29.96 in (1014.5 mb)
Dewpoint 38°F (3°C)
Visibility 10.00 mi
Wind Chill35°F (2°C)
Last update 22 Mar 5:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: A 30 percent chance of rain, mainly after 5pm. Mostly cloudy, with a high near 53. South wind 6 to 10 mph.

    High: 53 °F

    Chance Rain

  • Tonight

    Tonight: Rain, mainly between 8pm and 11pm, then showers after 11pm. Low around 38. South wind around 5 mph becoming light and variable. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 38 °F

    Rain

  • Monday

    Monday: A 40 percent chance of rain before 2pm. Cloudy, then gradually becoming mostly sunny, with a high near 45. North wind 11 to 13 mph.

    High: 45 °F

    Chance Rain

  • Monday Night

    Monday Night: Mostly clear, with a low around 30. Northwest wind 9 to 11 mph.

    Low: 30 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 45. Northwest wind around 7 mph becoming southwest in the afternoon.

    High: 45 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Increasing clouds, with a low around 34.

    Low: 34 °F

    Increasing
    Clouds

  • Wednesday

    Wednesday: Mostly cloudy, with a high near 49.

    High: 49 °F

    Mostly Cloudy

  • Wednesday Night

    Wednesday Night: A 30 percent chance of rain after 2am. Mostly cloudy, with a low around 38.

    Low: 38 °F

    Mostly Cloudy
    then Chance
    Rain

  • Thursday

    Thursday: A 30 percent chance of rain. Mostly cloudy, with a high near 51.

    High: 51 °F

    Chance Rain

Detailed Forecast

Today
A 30 percent chance of rain, mainly after 5pm. Mostly cloudy, with a high near 53. South wind 6 to 10 mph.
Tonight
Rain, mainly between 8pm and 11pm, then showers after 11pm. Low around 38. South wind around 5 mph becoming light and variable. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Monday
A 40 percent chance of rain before 2pm. Cloudy, then gradually becoming mostly sunny, with a high near 45. North wind 11 to 13 mph.
Monday Night
Mostly clear, with a low around 30. Northwest wind 9 to 11 mph.
Tuesday
Sunny, with a high near 45. Northwest wind around 7 mph becoming southwest in the afternoon.
Tuesday Night
Increasing clouds, with a low around 34.
Wednesday
Mostly cloudy, with a high near 49.
Wednesday Night
A 30 percent chance of rain after 2am. Mostly cloudy, with a low around 38.
Thursday
A 30 percent chance of rain. Mostly cloudy, with a high near 51.
Thursday Night
Rain likely, mainly after 2am. Mostly cloudy, with a low around 41. Chance of precipitation is 60%.
Friday
Rain likely. Partly sunny, with a high near 49. Chance of precipitation is 60%.
Friday Night
Partly cloudy, with a low around 26.
Saturday
Sunny, with a high near 41.
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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:
2:51 am EDT Mar 22, 2026
Forecast Valid:
6am EDT Mar 22, 2026-6pm EDT Mar 28, 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