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 40. Southeast wind around 6 mph.

    Low: 40 °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 53. South wind 8 to 11 mph. Chance of precipitation is 30%.

    High: 53 °F

    Chance
    Showers

  • Sunday Night

    Sunday Night: Rain. Low around 39. East wind 5 to 10 mph becoming west in the evening. Chance of precipitation is 90%. 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. Mostly cloudy, with a high near 44. North wind 13 to 15 mph.

    High: 44 °F

    Chance Rain

  • Monday Night

    Monday Night: Mostly clear, with a low around 33. North wind around 15 mph.

    Low: 33 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 44.

    High: 44 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 37.

    Low: 37 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Mostly cloudy, with a high near 49.

    High: 49 °F

    Mostly Cloudy

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 38.

    Low: 38 °F

    Mostly Cloudy

Detailed Forecast

Overnight
Mostly cloudy, with a low around 40. Southeast wind around 6 mph.
Sunday
A slight chance of showers before 11am, then a chance of showers after 5pm. Mostly cloudy, with a high near 53. South wind 8 to 11 mph. Chance of precipitation is 30%.
Sunday Night
Rain. Low around 39. East wind 5 to 10 mph becoming west in the evening. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Monday
A 40 percent chance of rain before 2pm. Mostly cloudy, with a high near 44. North wind 13 to 15 mph.
Monday Night
Mostly clear, with a low around 33. North wind around 15 mph.
Tuesday
Sunny, with a high near 44.
Tuesday Night
Mostly cloudy, with a low around 37.
Wednesday
Mostly cloudy, with a high near 49.
Wednesday Night
Mostly cloudy, with a low around 38.
Thursday
A chance of rain between 8am and 2pm. Partly sunny, with a high near 49. Chance of precipitation is 30%.
Thursday Night
Rain likely. Mostly cloudy, with a low around 41. Chance of precipitation is 60%.
Friday
Mostly sunny, with a high near 46.
Friday Night
Partly cloudy, with a low around 31.
Saturday
Mostly sunny, with a high near 42.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.96°N 73.08°W (Elev. 3 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