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.

A Few Clouds

50°F

10°C

Humidity 96%
Wind Speed Calm
Barometer 30.18 in (1021.8 mb)
Dewpoint 49°F (9°C)
Visibility 10.00 mi
Last update 4 Nov 5:56 am EST
Extended Forecast for

Port Jefferson NYSimilar City Names

  • Today

    Today: Patchy fog before 8am. Otherwise, sunny, with a high near 70. Southwest wind 5 to 10 mph.

    High: 70 °F

    Patchy Fog
    then Sunny

  • Tonight

    Tonight: Partly cloudy, with a low around 59. South wind around 8 mph.

    Low: 59 °F

    Partly Cloudy

  • Thursday

    Thursday: A 20 percent chance of showers. Mostly cloudy, with a high near 69. South wind 7 to 11 mph.

    High: 69 °F

    Slight Chance
    Showers

  • Thursday Night

    Thursday Night: Showers, mainly after 1am. Low around 61. South wind 7 to 10 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

    Low: 61 °F

    Chance
    Showers then
    Showers

  • Friday

    Friday: Showers, with thunderstorms also possible after 10am. High near 66. South wind around 7 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

    High: 66 °F

    Showers

  • Friday Night

    Friday Night: Showers and possibly a thunderstorm before 1am, then showers likely. Low around 57. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 57 °F

    Showers

  • Saturday

    Saturday: A 40 percent chance of showers before 1pm. Partly sunny, with a high near 64.

    High: 64 °F

    Chance
    Showers

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 49.

    Low: 49 °F

    Partly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 59.

    High: 59 °F

    Mostly Sunny

Detailed Forecast

Today
Patchy fog before 8am. Otherwise, sunny, with a high near 70. Southwest wind 5 to 10 mph.
Tonight
Partly cloudy, with a low around 59. South wind around 8 mph.
Thursday
A 20 percent chance of showers. Mostly cloudy, with a high near 69. South wind 7 to 11 mph.
Thursday Night
Showers, mainly after 1am. Low around 61. South wind 7 to 10 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Friday
Showers, with thunderstorms also possible after 10am. High near 66. South wind around 7 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.
Friday Night
Showers and possibly a thunderstorm before 1am, then showers likely. Low around 57. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Saturday
A 40 percent chance of showers before 1pm. Partly sunny, with a high near 64.
Saturday Night
Partly cloudy, with a low around 49.
Sunday
Mostly sunny, with a high near 59.
Sunday Night
Partly cloudy, with a low around 47.
Monday
A 30 percent chance of rain. Mostly sunny, with a high near 58.
Monday Night
A 30 percent chance of rain. Partly cloudy, with a low around 46.
Tuesday
Sunny, with a high near 59.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NYSimilar City Names
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
3:51 pm EST Nov 3, 2026
Forecast Valid:
6am EST Nov 4, 2026-6pm EST Nov 10, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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