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

79°F

26°C

Humidity 41%
Wind Speed S 9 mph
Barometer 30.10 in (1019.1 mb)
Dewpoint 53°F (12°C)
Visibility 10.00 mi
Heat Index79°F (26°C)
Last update 25 Jun 10:56 am EDT
Extended Forecast for

Stony Brook NY

  • Today

    Today: Mostly sunny, with a high near 83. South wind 5 to 8 mph.

    High: 83 °F

    Mostly Sunny

  • Tonight

    Tonight: Showers likely and possibly a thunderstorm after 2am. Increasing clouds, with a low around 66. South wind 7 to 9 mph. Chance of precipitation is 70%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

    Low: 66 °F

    Partly Cloudy
    then Showers
    Likely

  • Friday

    Friday: Showers likely and possibly a thunderstorm before 8am, then a slight chance of showers between 8am and 11am. Partly sunny, with a high near 82. Southwest wind around 8 mph. Chance of precipitation is 60%.

    High: 82 °F

    Showers
    Likely then
    Partly Sunny

  • Friday Night

    Friday Night: A 40 percent chance of showers after 2am. Mostly cloudy, with a low around 66. Southwest wind around 5 mph becoming calm in the evening.

    Low: 66 °F

    Mostly Cloudy
    then Chance
    Showers

  • Saturday

    Saturday: Showers likely, mainly between 8am and 2pm. Mostly cloudy, with a high near 77. Calm wind becoming east around 6 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

    High: 77 °F

    Showers
    Likely

  • Saturday Night

    Saturday Night: A 30 percent chance of showers before 8pm. Mostly cloudy, with a low around 65.

    Low: 65 °F

    Chance
    Showers then
    Mostly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 86.

    High: 86 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 66.

    Low: 66 °F

    Partly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 87.

    High: 87 °F

    Mostly Sunny

Detailed Forecast

Today
Mostly sunny, with a high near 83. South wind 5 to 8 mph.
Tonight
Showers likely and possibly a thunderstorm after 2am. Increasing clouds, with a low around 66. South wind 7 to 9 mph. Chance of precipitation is 70%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Friday
Showers likely and possibly a thunderstorm before 8am, then a slight chance of showers between 8am and 11am. Partly sunny, with a high near 82. Southwest wind around 8 mph. Chance of precipitation is 60%.
Friday Night
A 40 percent chance of showers after 2am. Mostly cloudy, with a low around 66. Southwest wind around 5 mph becoming calm in the evening.
Saturday
Showers likely, mainly between 8am and 2pm. Mostly cloudy, with a high near 77. Calm wind becoming east around 6 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.
Saturday Night
A 30 percent chance of showers before 8pm. Mostly cloudy, with a low around 65.
Sunday
Mostly sunny, with a high near 86.
Sunday Night
Partly cloudy, with a low around 66.
Monday
Mostly sunny, with a high near 87.
Monday Night
Partly cloudy, with a low around 68.
Tuesday
Mostly sunny, with a high near 90.
Tuesday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 71.
Wednesday
Mostly sunny, with a high near 92.
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ABOUT THIS FORECAST

 
Point Forecast:
Stony Brook NY
 40.9°N 73.12°W (Elev. 148 ft)
Last Update:
2:24 am EDT Jun 25, 2026
Forecast Valid:
11am EDT Jun 25, 2026-6pm EDT Jul 1, 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