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

75°F

24°C

Humidity 90%
Wind Speed S 6 mph
Barometer 30.08 in (1018.5 mb)
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Last update 14 Jul 12:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Patchy drizzle after 5am. Patchy fog. Otherwise, mostly cloudy, with a low around 71. Light south wind.

    Low: 71 °F

    Patchy
    Drizzle and
    Patchy Fog

  • Monday

    Monday: Patchy drizzle before 8am, then a slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 84. South wind 3 to 7 mph. Chance of precipitation is 20%.

    High: 84 °F

    Patchy
    Drizzle then
    Slight Chance
    T-storms

  • Monday Night

    Monday Night: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 73. Southwest wind 5 to 7 mph.

    Low: 73 °F

    Chance
    T-storms

  • Tuesday

    Tuesday: A chance of showers and thunderstorms. Mostly cloudy, with a high near 85. Calm wind becoming south around 5 mph in the afternoon. Chance of precipitation is 40%.

    High: 85 °F

    Chance
    Showers

  • Tuesday Night

    Tuesday Night: A 20 percent chance of showers after 2am. Partly cloudy, with a low around 73. Southwest wind 5 to 7 mph.

    Low: 73 °F

    Partly Cloudy
    then Slight
    Chance
    Showers

  • Wednesday

    Wednesday: Partly sunny, with a high near 88.

    High: 88 °F

    Partly Sunny

  • Wednesday Night

    Wednesday Night: A 30 percent chance of showers before 2am. Mostly cloudy, with a low around 75.

    Low: 75 °F

    Chance
    Showers

  • Thursday

    Thursday: A 30 percent chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 91.

    High: 91 °F

    Partly Sunny
    then Chance
    T-storms

  • Thursday Night

    Thursday Night: A 30 percent chance of showers and thunderstorms before 8pm. Mostly cloudy, with a low around 77.

    Low: 77 °F

    Chance
    T-storms then
    Mostly Cloudy

Detailed Forecast

Overnight
Patchy drizzle after 5am. Patchy fog. Otherwise, mostly cloudy, with a low around 71. Light south wind.
Monday
Patchy drizzle before 8am, then a slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 84. South wind 3 to 7 mph. Chance of precipitation is 20%.
Monday Night
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 73. Southwest wind 5 to 7 mph.
Tuesday
A chance of showers and thunderstorms. Mostly cloudy, with a high near 85. Calm wind becoming south around 5 mph in the afternoon. Chance of precipitation is 40%.
Tuesday Night
A 20 percent chance of showers after 2am. Partly cloudy, with a low around 73. Southwest wind 5 to 7 mph.
Wednesday
Partly sunny, with a high near 88.
Wednesday Night
A 30 percent chance of showers before 2am. Mostly cloudy, with a low around 75.
Thursday
A 30 percent chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 91.
Thursday Night
A 30 percent chance of showers and thunderstorms before 8pm. Mostly cloudy, with a low around 77.
Friday
A 30 percent chance of showers after 2pm. Mostly sunny, with a high near 91.
Friday Night
A 30 percent chance of showers. Partly cloudy, with a low around 74.
Saturday
A 30 percent chance of showers. Mostly sunny, with a high near 87.
Saturday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 71.
Sunday
Mostly sunny, with a high near 85.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
5:47 pm EDT Jul 13, 2025
Forecast Valid:
1am EDT Jul 14, 2025-6pm EDT Jul 20, 2025
 
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