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

34°F

1°C

Humidity 67%
Wind Speed E 3 mph
Barometer 30.44 in (1030.9 mb)
Dewpoint 24°F (-4°C)
Visibility 10.00 mi
Last update 15 Mar 5:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Today

    Today: Mostly cloudy, with a high near 46. Northeast wind 6 to 13 mph becoming southeast in the afternoon.

    High: 46 °F

    Mostly Cloudy

  • Tonight

    Tonight: Showers and possibly a thunderstorm, mainly after 5am. Patchy fog after 2am. Temperature falling to near 39 by 8pm, then rising to around 47 during the remainder of the night. Breezy, with a southeast wind 13 to 23 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

    Low: 39 °F⇑

    Mostly Cloudy
    then Showers
    and Patchy
    Fog

  • Monday

    Monday: Intermittent showers and thunderstorms. Patchy fog before noon. Otherwise, cloudy, with a high near 56. Windy, with a south wind 26 to 30 mph. Chance of precipitation is 50%.

    High: 56 °F

    Intermittent
    T-storms and
    Patchy Fog

  • Monday Night

    Monday Night: Periods of showers and possibly a thunderstorm before 2am, then a chance of showers. Some of the storms could produce heavy rainfall. Low around 35. Very windy, with a south wind 34 to 41 mph becoming west after midnight. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.

    Low: 35 °F

    Heavy Rain
    and Very
    Windy

  • Tuesday

    Tuesday: A 30 percent chance of showers before 8am. Mostly sunny, with a steady temperature around 37. Breezy, with a west wind 23 to 25 mph.

    High: 37 °F

    Breezy.
    Chance
    Showers then
    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 27. Breezy.

    Low: 27 °F

    Partly Cloudy
    and Breezy

  • Wednesday

    Wednesday: Increasing clouds, with a high near 37.

    High: 37 °F

    Increasing
    Clouds

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 32.

    Low: 32 °F

    Mostly Cloudy

  • Thursday

    Thursday: Partly sunny, with a high near 43.

    High: 43 °F

    Partly Sunny

Detailed Forecast

Today
Mostly cloudy, with a high near 46. Northeast wind 6 to 13 mph becoming southeast in the afternoon.
Tonight
Showers and possibly a thunderstorm, mainly after 5am. Patchy fog after 2am. Temperature falling to near 39 by 8pm, then rising to around 47 during the remainder of the night. Breezy, with a southeast wind 13 to 23 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.
Monday
Intermittent showers and thunderstorms. Patchy fog before noon. Otherwise, cloudy, with a high near 56. Windy, with a south wind 26 to 30 mph. Chance of precipitation is 50%.
Monday Night
Periods of showers and possibly a thunderstorm before 2am, then a chance of showers. Some of the storms could produce heavy rainfall. Low around 35. Very windy, with a south wind 34 to 41 mph becoming west after midnight. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.
Tuesday
A 30 percent chance of showers before 8am. Mostly sunny, with a steady temperature around 37. Breezy, with a west wind 23 to 25 mph.
Tuesday Night
Partly cloudy, with a low around 27. Breezy.
Wednesday
Increasing clouds, with a high near 37.
Wednesday Night
Mostly cloudy, with a low around 32.
Thursday
Partly sunny, with a high near 43.
Thursday Night
Mostly cloudy, with a low around 35.
Friday
Mostly sunny, with a high near 47.
Friday Night
A 40 percent chance of rain. Mostly cloudy, with a low around 37.
Saturday
A 50 percent chance of rain. Partly sunny, with a high near 46.
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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:
6:56 am EDT Mar 15, 2026
Forecast Valid:
6am EDT Mar 15, 2026-6pm EDT Mar 21, 2026
 
Forecast Discussion
 
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Additional Resources

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Hourly Weather Forecast

National Digital Forecast Database

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation