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

28°F

-2°C

Humidity 75%
Wind Speed Calm
Barometer 30.32 in (1026.7 mb)
Dewpoint 21°F (-6°C)
Visibility 10.00 mi
Last update 19 Mar 5:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Mostly sunny, with a high near 43. Calm wind becoming south around 6 mph in the afternoon.

    High: 43 °F

    Mostly Sunny

  • Tonight

    Tonight: Partly cloudy, with a low around 33. Light south wind.

    Low: 33 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 50. Calm wind becoming south 5 to 9 mph in the afternoon.

    High: 50 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Rain likely. Mostly cloudy, with a low around 40. South wind around 10 mph, with gusts as high as 26 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 40 °F

    Rain Likely

  • Saturday

    Saturday: Mostly sunny, with a high near 54. West wind 6 to 9 mph.

    High: 54 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 39.

    Low: 39 °F

    Mostly Cloudy

  • Sunday

    Sunday: Partly sunny, with a high near 54.

    High: 54 °F

    Partly Sunny

  • Sunday Night

    Sunday Night: Rain likely, mainly after 2am. Mostly cloudy, with a low around 37. Chance of precipitation is 60%.

    Low: 37 °F

    Rain Likely

  • Monday

    Monday: Rain likely, mainly before 8am. Mostly cloudy, with a high near 47. Chance of precipitation is 60%.

    High: 47 °F

    Rain Likely
    then Chance
    Rain

Detailed Forecast

Today
Mostly sunny, with a high near 43. Calm wind becoming south around 6 mph in the afternoon.
Tonight
Partly cloudy, with a low around 33. Light south wind.
Friday
Mostly sunny, with a high near 50. Calm wind becoming south 5 to 9 mph in the afternoon.
Friday Night
Rain likely. Mostly cloudy, with a low around 40. South wind around 10 mph, with gusts as high as 26 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.
Saturday
Mostly sunny, with a high near 54. West wind 6 to 9 mph.
Saturday Night
Mostly cloudy, with a low around 39.
Sunday
Partly sunny, with a high near 54.
Sunday Night
Rain likely, mainly after 2am. Mostly cloudy, with a low around 37. Chance of precipitation is 60%.
Monday
Rain likely, mainly before 8am. Mostly cloudy, with a high near 47. Chance of precipitation is 60%.
Monday Night
Mostly clear, with a low around 27.
Tuesday
Mostly sunny, with a high near 42.
Tuesday Night
Partly cloudy, with a low around 32.
Wednesday
Partly sunny, with a high near 48.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.93°N 73.06°W (Elev. 161 ft)
Last Update:
2:26 am EDT Mar 19, 2026
Forecast Valid:
6am EDT Mar 19, 2026-6pm EDT Mar 25, 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