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

17°C

63°F

Humidity 84%
Wind Speed SW 7 km/h
Barometer 1019.3 mb (30.10 in)
Dewpoint 14°C (58°F)
Visibility 16 km
Last update 17 May 11:56 pm EDT
Extended Forecast for

Port Jefferson NY

  • Overnight

    Overnight: Partly cloudy, with a low around 17. Calm wind.

    Low: 17 °C

    Partly Cloudy

  • Monday

    Monday: Sunny, with a high near 27. East wind around 14 km/h.

    High: 27 °C

    Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 18. South wind 11 to 13 km/h.

    Low: 18 °C

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 31. Southwest wind 11 to 16 km/h increasing to 18 to 23 km/h in the afternoon.

    High: 31 °C

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 19. Southwest wind 18 to 23 km/h.

    Low: 19 °C

    Partly Cloudy

  • Wednesday

    Wednesday: Showers and possibly a thunderstorm after 2pm. High near 30. Chance of precipitation is 80%. New rainfall amounts between 1 and 2.5 mm, except higher amounts possible in thunderstorms.

    High: 30 °C

    Sunny then
    Showers

  • Wednesday Night

    Wednesday Night: Showers and possibly a thunderstorm before 8pm, then a chance of showers between 8pm and 2am. Low around 14. Chance of precipitation is 80%.

    Low: 14 °C

    Showers then
    Chance
    Showers

  • Thursday

    Thursday: Partly sunny, with a high near 20.

    High: 20 °C

    Partly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 12.

    Low: 12 °C

    Partly Cloudy

Detailed Forecast

Overnight
Partly cloudy, with a low around 17. Calm wind.
Monday
Sunny, with a high near 27. East wind around 14 km/h.
Monday Night
Partly cloudy, with a low around 18. South wind 11 to 13 km/h.
Tuesday
Mostly sunny, with a high near 31. Southwest wind 11 to 16 km/h increasing to 18 to 23 km/h in the afternoon.
Tuesday Night
Partly cloudy, with a low around 19. Southwest wind 18 to 23 km/h.
Wednesday
Showers and possibly a thunderstorm after 2pm. High near 30. Chance of precipitation is 80%. New rainfall amounts between 1 and 2.5 mm, except higher amounts possible in thunderstorms.
Wednesday Night
Showers and possibly a thunderstorm before 8pm, then a chance of showers between 8pm and 2am. Low around 14. Chance of precipitation is 80%.
Thursday
Partly sunny, with a high near 20.
Thursday Night
Partly cloudy, with a low around 12.
Friday
Partly sunny, with a high near 19.
Friday Night
A 50 percent chance of showers. Mostly cloudy, with a low around 11.
Saturday
Showers likely. Mostly cloudy, with a high near 18. Chance of precipitation is 60%.
Saturday Night
A 50 percent chance of showers. Mostly cloudy, with a low around 13.
Sunday
A 50 percent chance of showers. Mostly cloudy, with a high near 21.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NY
 40.95°N 73.05°W (Elev. 151 m)
Last Update:
3:04 pm EDT May 17, 2026
Forecast Valid:
12am EDT May 18, 2026-6pm EDT May 24, 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