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

43°F

6°C

Humidity 89%
Wind Speed SE 13 mph
Barometer 29.98 in (1015.4 mb)
Dewpoint 40°F (4°C)
Visibility 9.00 mi
Wind Chill36°F (2°C)
Last update 22 Mar 1:56 am EDT
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Mostly cloudy, with a low around 39. Southeast wind around 5 mph.

    Low: 39 °F

    Mostly Cloudy

  • Sunday

    Sunday: A slight chance of showers before 11am, then a chance of showers after 5pm. Mostly cloudy, with a high near 57. South wind 7 to 10 mph. Chance of precipitation is 30%.

    High: 57 °F

    Chance
    Showers

  • Sunday Night

    Sunday Night: Rain. Low around 39. Light and variable wind becoming north around 6 mph in the evening. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 39 °F

    Rain

  • Monday

    Monday: A 40 percent chance of rain before 2pm. Cloudy, with a high near 45. North wind around 10 mph.

    High: 45 °F

    Chance Rain

  • Monday Night

    Monday Night: Mostly clear, with a low around 31. Northwest wind around 9 mph.

    Low: 31 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 45.

    High: 45 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 34.

    Low: 34 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Partly sunny, with a high near 50.

    High: 50 °F

    Partly Sunny

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 35.

    Low: 35 °F

    Mostly Cloudy

Detailed Forecast

Overnight
Mostly cloudy, with a low around 39. Southeast wind around 5 mph.
Sunday
A slight chance of showers before 11am, then a chance of showers after 5pm. Mostly cloudy, with a high near 57. South wind 7 to 10 mph. Chance of precipitation is 30%.
Sunday Night
Rain. Low around 39. Light and variable wind becoming north around 6 mph in the evening. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.
Monday
A 40 percent chance of rain before 2pm. Cloudy, with a high near 45. North wind around 10 mph.
Monday Night
Mostly clear, with a low around 31. Northwest wind around 9 mph.
Tuesday
Sunny, with a high near 45.
Tuesday Night
Mostly cloudy, with a low around 34.
Wednesday
Partly sunny, with a high near 50.
Wednesday Night
Mostly cloudy, with a low around 35.
Thursday
A chance of rain between 8am and 2pm. Partly sunny, with a high near 50. Chance of precipitation is 30%.
Thursday Night
Rain likely. Mostly cloudy, with a low around 40. Chance of precipitation is 60%.
Friday
Mostly sunny, with a high near 49.
Friday Night
Partly cloudy, with a low around 28.
Saturday
Mostly sunny, with a high near 43.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.93°N 73.06°W (Elev. 161 ft)
Last Update:
3:03 pm EDT Mar 21, 2026
Forecast Valid:
2am EDT Mar 22, 2026-6pm EDT Mar 28, 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