National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Hazardous Weather Conditions

Current conditions at

Islip, Long Island Mac Arthur Airport (KISP)

Lat: 40.79°NLon: 73.1°WElev: 98ft.

Partly Cloudy

78°F

26°C

Humidity 85%
Wind Speed S 6 mph
Barometer 30.06 in (1017.6 mb)
Dewpoint 73°F (23°C)
Visibility 10.00 mi
Heat Index80°F (27°C)
Last update 15 Jul 3:56 pm EDT
Extended Forecast for

Port Jefferson NY

Heat Advisory July 16, 11:00am until July 17, 10:00pm
Click here for hazard details and duration
Heat Advisory

  • This Afternoon

    This Afternoon: A 20 percent chance of showers and thunderstorms before 5pm. Sunny, with a high near 86. South wind 3 to 5 mph.

    High: 86 °F

    Slight Chance
    T-storms

  • Tonight

    Tonight: Patchy fog before 3am, then patchy fog after 5am. Otherwise, increasing clouds, with a low around 73. South wind around 5 mph becoming calm in the evening.

    Low: 73 °F

    Mostly Clear
    then Patchy
    Fog

  • Wednesday

    Wednesday: Patchy fog before 7am. Otherwise, mostly sunny, with a high near 88. Heat index values as high as 95. Calm wind becoming south around 6 mph in the afternoon.

    High: 88 °F

    Patchy Fog
    then Mostly
    Sunny

  • Wednesday Night

    Wednesday Night: A 50 percent chance of showers and thunderstorms. Increasing clouds, with a low around 75. South wind 7 to 9 mph.

    Low: 75 °F

    Chance
    T-storms

  • Thursday

    Thursday: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 2pm. Partly sunny, with a high near 88. Southwest wind 7 to 10 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    High: 88 °F

    Showers
    Likely

  • Thursday Night

    Thursday Night: Showers likely and possibly a thunderstorm before 8pm. Partly cloudy, with a low around 76. Chance of precipitation is 60%.

    Low: 76 °F

    Showers
    Likely then
    Partly Cloudy

  • Friday

    Friday: Sunny, with a high near 88.

    High: 88 °F

    Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 69.

    Low: 69 °F

    Mostly Clear

  • Saturday

    Saturday: Sunny, with a high near 84.

    High: 84 °F

    Sunny

Detailed Forecast

This Afternoon
A 20 percent chance of showers and thunderstorms before 5pm. Sunny, with a high near 86. South wind 3 to 5 mph.
Tonight
Patchy fog before 3am, then patchy fog after 5am. Otherwise, increasing clouds, with a low around 73. South wind around 5 mph becoming calm in the evening.
Wednesday
Patchy fog before 7am. Otherwise, mostly sunny, with a high near 88. Heat index values as high as 95. Calm wind becoming south around 6 mph in the afternoon.
Wednesday Night
A 50 percent chance of showers and thunderstorms. Increasing clouds, with a low around 75. South wind 7 to 9 mph.
Thursday
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 2pm. Partly sunny, with a high near 88. Southwest wind 7 to 10 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Thursday Night
Showers likely and possibly a thunderstorm before 8pm. Partly cloudy, with a low around 76. Chance of precipitation is 60%.
Friday
Sunny, with a high near 88.
Friday Night
Mostly clear, with a low around 69.
Saturday
Sunny, with a high near 84.
Saturday Night
Partly cloudy, with a low around 71.
Sunday
A 50 percent chance of showers. Partly sunny, with a high near 84.
Sunday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 71.
Monday
Mostly sunny, with a high near 85.
Monday Night
Partly cloudy, with a low around 69.
Tuesday
Mostly sunny, with a high near 83.
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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:
3:16 pm EDT Jul 15, 2025
Forecast Valid:
4pm EDT Jul 15, 2025-6pm EDT Jul 22, 2025
 
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