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.

Mostly Cloudy

38°F

3°C

Humidity 83%
Wind Speed SW 9 mph
Barometer 30.14 in (1020.5 mb)
Dewpoint 33°F (1°C)
Visibility 10.00 mi
Wind Chill32°F (0°C)
Last update 20 Mar 3:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: A 30 percent chance of rain after 5pm. Mostly sunny, with a high near 48. South wind 5 to 10 mph increasing to 11 to 16 mph in the afternoon.

    High: 48 °F

    Mostly Sunny
    then Chance
    Rain

  • Tonight

    Tonight: Rain, mainly before 2am. Low around 43. Breezy, with a south wind 13 to 23 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 43 °F

    Rain and
    Breezy

  • Saturday

    Saturday: Sunny, with a high near 49. Northwest wind around 11 mph.

    High: 49 °F

    Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 40. North wind around 7 mph becoming southeast after midnight.

    Low: 40 °F

    Mostly Cloudy

  • Sunday

    Sunday: A 20 percent chance of rain. Mostly cloudy, with a high near 50. South wind 8 to 13 mph.

    High: 50 °F

    Slight Chance
    Rain

  • Sunday Night

    Sunday Night: Rain likely, mainly after 2am. Cloudy, with a low around 41. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 41 °F

    Rain Likely

  • Monday

    Monday: Rain likely, mainly before 8am. Cloudy, then gradually becoming mostly sunny, with a high near 44. Chance of precipitation is 60%.

    High: 44 °F

    Rain Likely

  • Monday Night

    Monday Night: Partly cloudy, with a low around 32.

    Low: 32 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Sunny, with a high near 42.

    High: 42 °F

    Sunny

Detailed Forecast

Today
A 30 percent chance of rain after 5pm. Mostly sunny, with a high near 48. South wind 5 to 10 mph increasing to 11 to 16 mph in the afternoon.
Tonight
Rain, mainly before 2am. Low around 43. Breezy, with a south wind 13 to 23 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Saturday
Sunny, with a high near 49. Northwest wind around 11 mph.
Saturday Night
Mostly cloudy, with a low around 40. North wind around 7 mph becoming southeast after midnight.
Sunday
A 20 percent chance of rain. Mostly cloudy, with a high near 50. South wind 8 to 13 mph.
Sunday Night
Rain likely, mainly after 2am. Cloudy, with a low around 41. 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 44. Chance of precipitation is 60%.
Monday Night
Partly cloudy, with a low around 32.
Tuesday
Sunny, with a high near 42.
Tuesday Night
Mostly cloudy, with a low around 36.
Wednesday
Mostly cloudy, with a high near 46.
Wednesday Night
Mostly cloudy, with a low around 34.
Thursday
A 30 percent chance of rain. Partly sunny, with a high near 47.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
2:26 am EDT Mar 20, 2026
Forecast Valid:
4am EDT Mar 20, 2026-6pm EDT Mar 26, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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