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.

Fair

77°F

25°C

Humidity 96%
Wind Speed Calm
Barometer 30.04 in (1017.3 mb)
Dewpoint 76°F (24°C)
Visibility 10.00 mi
Heat Index78°F (26°C)
Last update 16 Jul 1:56 am 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

  • Overnight

    Overnight: Patchy fog before 3am, then patchy fog after 5am. Otherwise, partly cloudy, with a low around 73. Calm wind.

    Low: 73 °F

    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 Sunny

  • Wednesday Night

    Wednesday Night: A 30 percent chance of showers and thunderstorms, mainly between 2am and 5am. Mostly cloudy, with a low around 75. Southwest wind 6 to 8 mph.

    Low: 75 °F

    Mostly Cloudy
    then Chance
    Showers

  • Thursday

    Thursday: A 50 percent chance of showers and thunderstorms, mainly after 8am. Partly sunny, with a high near 88. Heat index values as high as 96. Southwest wind 7 to 10 mph.

    High: 88 °F

    Chance
    T-storms

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 76. Southwest wind around 9 mph.

    Low: 76 °F

    Partly Cloudy

  • Friday

    Friday: Sunny, with a high near 86.

    High: 86 °F

    Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 68.

    Low: 68 °F

    Partly Cloudy

  • Saturday

    Saturday: Mostly sunny, with a high near 83.

    High: 83 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: A 30 percent chance of showers after 2am. Mostly cloudy, with a low around 71.

    Low: 71 °F

    Mostly Cloudy
    then Chance
    Showers

Detailed Forecast

Overnight
Patchy fog before 3am, then patchy fog after 5am. Otherwise, partly cloudy, with a low around 73. Calm wind.
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 30 percent chance of showers and thunderstorms, mainly between 2am and 5am. Mostly cloudy, with a low around 75. Southwest wind 6 to 8 mph.
Thursday
A 50 percent chance of showers and thunderstorms, mainly after 8am. Partly sunny, with a high near 88. Heat index values as high as 96. Southwest wind 7 to 10 mph.
Thursday Night
Partly cloudy, with a low around 76. Southwest wind around 9 mph.
Friday
Sunny, with a high near 86.
Friday Night
Partly cloudy, with a low around 68.
Saturday
Mostly sunny, with a high near 83.
Saturday Night
A 30 percent chance of showers after 2am. Mostly cloudy, with a low around 71.
Sunday
A chance of showers, then showers likely and possibly a thunderstorm after 2pm. Mostly cloudy, with a high near 84. Chance of precipitation is 60%.
Sunday Night
Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 70. Chance of precipitation is 60%.
Monday
Mostly sunny, with a high near 83.
Monday Night
Partly cloudy, with a low around 68.
Tuesday
Mostly sunny, with a high near 82.
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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:
2:02 am EDT Jul 16, 2025
Forecast Valid:
2am EDT Jul 16, 2025-6pm EDT Jul 22, 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