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.

Fair

45°F

7°C

Humidity 97%
Wind Speed Calm
Barometer 29.76 in (1007.8 mb)
Dewpoint 44°F (7°C)
Visibility 10.00 mi
Last update 12 Nov 1:56 am EST
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Mostly cloudy, with a low around 51. East wind 5 to 7 mph.

    Low: 51 °F

    Mostly Cloudy

  • Thursday

    Thursday: Rain, mainly after 1pm. High near 59. East wind 9 to 17 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

    High: 59 °F

    Chance Rain
    then Rain

  • Thursday Night

    Thursday Night: Rain. Low around 42. Breezy, with a northeast wind around 22 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 42 °F

    Rain and
    Breezy

  • Friday

    Friday: Rain. High near 48. Breezy, with a north wind 15 to 22 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

    High: 48 °F

    Rain and
    Breezy

  • Friday Night

    Friday Night: A 20 percent chance of rain. Mostly cloudy, with a low around 39. North wind around 13 mph.

    Low: 39 °F

    Slight Chance
    Rain

  • Saturday

    Saturday: Partly sunny, with a high near 48.

    High: 48 °F

    Partly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 39.

    Low: 39 °F

    Partly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 50.

    High: 50 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 40.

    Low: 40 °F

    Partly Cloudy

Detailed Forecast

Overnight
Mostly cloudy, with a low around 51. East wind 5 to 7 mph.
Thursday
Rain, mainly after 1pm. High near 59. East wind 9 to 17 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Thursday Night
Rain. Low around 42. Breezy, with a northeast wind around 22 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.
Friday
Rain. High near 48. Breezy, with a north wind 15 to 22 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Friday Night
A 20 percent chance of rain. Mostly cloudy, with a low around 39. North wind around 13 mph.
Saturday
Partly sunny, with a high near 48.
Saturday Night
Partly cloudy, with a low around 39.
Sunday
Mostly sunny, with a high near 50.
Sunday Night
Partly cloudy, with a low around 40.
Monday
Sunny, with a high near 51.
Monday Night
Mostly clear, with a low around 39.
Tuesday
Sunny, with a high near 52.
Tuesday Night
Mostly clear, with a low around 41.
Wednesday
Sunny, with a high near 56.
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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:
1:27 am EST Nov 12, 2026
Forecast Valid:
2am EST Nov 12, 2026-6pm EST Nov 18, 2026
 
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