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

38°F

3°C

Humidity 52%
Wind Speed E 8 mph
Barometer 30.10 in (1019.1 mb)
Dewpoint 22°F (-6°C)
Visibility 10.00 mi
Wind Chill32°F (0°C)
Last update 19 Feb 10:56 am EST
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Mostly cloudy, with a high near 39. East wind 7 to 10 mph.

    High: 39 °F

    Mostly Cloudy

  • Tonight

    Tonight: A 50 percent chance of rain after 4am. Cloudy, with a low around 32. Light east wind increasing to 5 to 10 mph in the evening.

    Low: 32 °F

    Cloudy then
    Chance Rain

  • Friday

    Friday: Rain, mainly after 7am. High near 39. East wind 11 to 16 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

    High: 39 °F

    Rain

  • Friday Night

    Friday Night: A 50 percent chance of rain, mainly before 1am. Mostly cloudy, with a low around 35. Northeast wind 6 to 13 mph becoming northwest after midnight.

    Low: 35 °F

    Chance Rain

  • Saturday

    Saturday: A slight chance of rain and snow before 10am, then a slight chance of snow between 10am and 1pm, then a slight chance of rain and snow after 1pm. Mostly cloudy, with a high near 40. Northwest wind 6 to 8 mph becoming east in the afternoon. Chance of precipitation is 20%.

    High: 40 °F

    Slight Chance
    Rain/Snow

  • Saturday Night

    Saturday Night: A 30 percent chance of snow before 1am. Mostly cloudy, with a low around 31.

    Low: 31 °F

    Chance Snow

  • Sunday

    Sunday: A 40 percent chance of snow after 1pm. Mostly cloudy, with a high near 35.

    High: 35 °F

    Mostly Cloudy
    then Chance
    Snow

  • Sunday Night

    Sunday Night: A 50 percent chance of snow. Cloudy, with a low around 30. Blustery.

    Low: 30 °F

    Chance Snow
    and Blustery

  • Monday

    Monday: A 30 percent chance of snow before 1pm. Mostly cloudy, with a high near 35. Breezy.

    High: 35 °F

    Chance Snow
    and Breezy

Detailed Forecast

Today
Mostly cloudy, with a high near 39. East wind 7 to 10 mph.
Tonight
A 50 percent chance of rain after 4am. Cloudy, with a low around 32. Light east wind increasing to 5 to 10 mph in the evening.
Friday
Rain, mainly after 7am. High near 39. East wind 11 to 16 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Friday Night
A 50 percent chance of rain, mainly before 1am. Mostly cloudy, with a low around 35. Northeast wind 6 to 13 mph becoming northwest after midnight.
Saturday
A slight chance of rain and snow before 10am, then a slight chance of snow between 10am and 1pm, then a slight chance of rain and snow after 1pm. Mostly cloudy, with a high near 40. Northwest wind 6 to 8 mph becoming east in the afternoon. Chance of precipitation is 20%.
Saturday Night
A 30 percent chance of snow before 1am. Mostly cloudy, with a low around 31.
Sunday
A 40 percent chance of snow after 1pm. Mostly cloudy, with a high near 35.
Sunday Night
A 50 percent chance of snow. Cloudy, with a low around 30. Blustery.
Monday
A 30 percent chance of snow before 1pm. Mostly cloudy, with a high near 35. Breezy.
Monday Night
Mostly cloudy, with a low around 27.
Tuesday
Sunny, with a high near 35.
Tuesday Night
Partly cloudy, with a low around 26.
Wednesday
Mostly cloudy, with a high near 38.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 ft)
Last Update:
10:22 am EST Feb 19, 2026
Forecast Valid:
11am EST Feb 19, 2026-6pm EST Feb 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