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.

Mostly Cloudy

55°F

13°C

Humidity 87%
Wind Speed NE 6 mph
Barometer 30.32 in (1026.6 mb)
Dewpoint 51°F (11°C)
Visibility 10.00 mi
Wind Chill54°F (12°C)
Last update 21 Sep 6:56 am EDT
Extended Forecast for

Port Jefferson NYSimilar City Names

  • Today

    Today: Partly sunny, with a high near 69. East wind 8 to 10 mph.

    High: 69 °F

    Partly Sunny

  • Tonight

    Tonight: Mostly clear, with a low around 56. East wind 3 to 7 mph.

    Low: 56 °F

    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 74. East wind 3 to 5 mph.

    High: 74 °F

    Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 63. Southwest wind around 6 mph.

    Low: 63 °F

    Partly Cloudy

  • Tuesday

    Tuesday: A chance of showers between 2pm and 5pm, then a chance of showers and thunderstorms after 5pm. Mostly sunny, with a high near 79. Southwest wind 6 to 8 mph. Chance of precipitation is 30%.

    High: 79 °F

    Mostly Sunny
    then Chance
    Showers

  • Tuesday Night

    Tuesday Night: Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 65. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 65 °F

    Showers
    Likely

  • Wednesday

    Wednesday: A 40 percent chance of showers. Partly sunny, with a high near 76.

    High: 76 °F

    Chance
    Showers

  • Wednesday Night

    Wednesday Night: A 40 percent chance of showers. Mostly cloudy, with a low around 62.

    Low: 62 °F

    Chance
    Showers

  • Thursday

    Thursday: A 30 percent chance of showers. Partly sunny, with a high near 70.

    High: 70 °F

    Chance
    Showers

Detailed Forecast

Today
Partly sunny, with a high near 69. East wind 8 to 10 mph.
Tonight
Mostly clear, with a low around 56. East wind 3 to 7 mph.
Monday
Sunny, with a high near 74. East wind 3 to 5 mph.
Monday Night
Partly cloudy, with a low around 63. Southwest wind around 6 mph.
Tuesday
A chance of showers between 2pm and 5pm, then a chance of showers and thunderstorms after 5pm. Mostly sunny, with a high near 79. Southwest wind 6 to 8 mph. Chance of precipitation is 30%.
Tuesday Night
Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 65. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Wednesday
A 40 percent chance of showers. Partly sunny, with a high near 76.
Wednesday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 62.
Thursday
A 30 percent chance of showers. Partly sunny, with a high near 70.
Thursday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 61.
Friday
A 30 percent chance of showers. Partly sunny, with a high near 73.
Friday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 64.
Saturday
A 40 percent chance of showers. Partly sunny, with a high near 74.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Port Jefferson NYSimilar City Names
 40.95°N 73.05°W (Elev. 151 ft)
Last Update:
5:49 am EDT Sep 21, 2025
Forecast Valid:
7am EDT Sep 21, 2025-6pm EDT Sep 27, 2025
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation