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

39°F

4°C

Humidity 65%
Wind Speed S 9 mph
Barometer 30.21 in (1023.0 mb)
Dewpoint 28°F (-2°C)
Visibility 10.00 mi
Wind Chill33°F (1°C)
Last update 19 Mar 3:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Tonight

    Tonight: Mostly cloudy, with a low around 34. South wind around 5 mph.

    Low: 34 °F

    Mostly Cloudy

  • Friday

    Friday: A 40 percent chance of rain after 2pm. Mostly sunny, with a high near 51. Light and variable wind becoming south 5 to 10 mph in the afternoon. Winds could gust as high as 22 mph.

    High: 51 °F

    Mostly Sunny
    then Chance
    Rain

  • Friday Night

    Friday Night: Rain likely, mainly between 8pm and 2am. Mostly cloudy, with a low around 41. South wind 7 to 13 mph, with gusts as high as 25 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 41 °F

    Rain Likely

  • Saturday

    Saturday: Mostly sunny, with a high near 54. Northwest wind 6 to 8 mph.

    High: 54 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 38. Northwest wind around 5 mph becoming light and variable after midnight.

    Low: 38 °F

    Mostly Cloudy

  • Sunday

    Sunday: Mostly cloudy, with a high near 53.

    High: 53 °F

    Mostly Cloudy

  • Sunday Night

    Sunday Night: Rain likely, mainly after 2am. Mostly cloudy, with a low around 40. Chance of precipitation is 60%.

    Low: 40 °F

    Rain Likely

  • Monday

    Monday: Rain likely, mainly before 8am. Partly sunny, with a high near 53. Chance of precipitation is 60%.

    High: 53 °F

    Rain Likely
    then Chance
    Rain

  • Monday Night

    Monday Night: Mostly clear, with a low around 29.

    Low: 29 °F

    Mostly Clear

Detailed Forecast

Tonight
Mostly cloudy, with a low around 34. South wind around 5 mph.
Friday
A 40 percent chance of rain after 2pm. Mostly sunny, with a high near 51. Light and variable wind becoming south 5 to 10 mph in the afternoon. Winds could gust as high as 22 mph.
Friday Night
Rain likely, mainly between 8pm and 2am. Mostly cloudy, with a low around 41. South wind 7 to 13 mph, with gusts as high as 25 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. Northwest wind 6 to 8 mph.
Saturday Night
Mostly cloudy, with a low around 38. Northwest wind around 5 mph becoming light and variable after midnight.
Sunday
Mostly cloudy, with a high near 53.
Sunday Night
Rain likely, mainly after 2am. Mostly cloudy, with a low around 40. Chance of precipitation is 60%.
Monday
Rain likely, mainly before 8am. Partly sunny, with a high near 53. Chance of precipitation is 60%.
Monday Night
Mostly clear, with a low around 29.
Tuesday
Sunny, with a high near 43.
Tuesday Night
Mostly cloudy, with a low around 33.
Wednesday
Partly sunny, with a high near 46.
Wednesday Night
Mostly cloudy, with a low around 32.
Thursday
Partly sunny, with a high near 49.
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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:
2:27 pm EDT Mar 19, 2026
Forecast Valid:
4pm EDT Mar 19, 2026-6pm EDT Mar 26, 2026
 
Forecast Discussion
 
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Additional Resources

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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