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.

A Few Clouds

34°F

1°C

Humidity 92%
Wind Speed SW 5 mph
Barometer 30.12 in (1019.9 mb)
Dewpoint 32°F (0°C)
Visibility 10.00 mi
Wind Chill29°F (-2°C)
Last update 20 Mar 6:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: A 30 percent chance of rain after 5pm. Mostly sunny, with a high near 50. Light southwest wind becoming south 8 to 13 mph in the morning.

    High: 50 °F

    Mostly Sunny
    then Chance
    Rain

  • Tonight

    Tonight: Rain, mainly before 2am. Low around 41. South wind 7 to 14 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 41 °F

    Rain

  • Saturday

    Saturday: Sunny, with a high near 51. Northwest wind 7 to 9 mph.

    High: 51 °F

    Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 37. North wind around 5 mph becoming light and variable in the evening.

    Low: 37 °F

    Mostly Cloudy

  • Sunday

    Sunday: A 20 percent chance of rain. Mostly cloudy, with a high near 52. South wind 6 to 10 mph.

    High: 52 °F

    Slight Chance
    Rain

  • Sunday Night

    Sunday Night: Rain likely, mainly after 2am. Cloudy, with a low around 40. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 40 °F

    Rain Likely

  • Monday

    Monday: Rain likely, mainly before 8am. Cloudy, then gradually becoming mostly sunny, with a high near 47. Chance of precipitation is 60%.

    High: 47 °F

    Rain Likely

  • Monday Night

    Monday Night: Partly cloudy, with a low around 30.

    Low: 30 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Sunny, with a high near 44.

    High: 44 °F

    Sunny

Detailed Forecast

Today
A 30 percent chance of rain after 5pm. Mostly sunny, with a high near 50. Light southwest wind becoming south 8 to 13 mph in the morning.
Tonight
Rain, mainly before 2am. Low around 41. South wind 7 to 14 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Saturday
Sunny, with a high near 51. Northwest wind 7 to 9 mph.
Saturday Night
Mostly cloudy, with a low around 37. North wind around 5 mph becoming light and variable in the evening.
Sunday
A 20 percent chance of rain. Mostly cloudy, with a high near 52. South wind 6 to 10 mph.
Sunday Night
Rain likely, mainly after 2am. Cloudy, with a low around 40. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.
Monday
Rain likely, mainly before 8am. Cloudy, then gradually becoming mostly sunny, with a high near 47. Chance of precipitation is 60%.
Monday Night
Partly cloudy, with a low around 30.
Tuesday
Sunny, with a high near 44.
Tuesday Night
Mostly cloudy, with a low around 34.
Wednesday
Partly sunny, with a high near 48.
Wednesday Night
Mostly cloudy, with a low around 32.
Thursday
A 30 percent chance of rain. 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 20, 2026
Forecast Valid:
7am EDT Mar 20, 2026-6pm EDT Mar 26, 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