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

78°F

26°C

Humidity 90%
Wind Speed SW 14 mph
Barometer 29.78 in (1008.2 mb)
Dewpoint 75°F (24°C)
Visibility 9.00 mi
Heat Index80°F (27°C)
Last update 3 Aug 4:56 pm EDT
Extended Forecast for

Stony Brook NY

  • This Afternoon

    This Afternoon: A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 81. Southwest wind around 11 mph, with gusts as high as 21 mph.

    High: 81 °F

    Chance
    Showers

  • Tonight

    Tonight: A chance of showers and thunderstorms before 8pm, then a slight chance of showers between 8pm and 11pm. Mostly cloudy, then gradually becoming mostly clear, with a low around 66. North wind 5 to 10 mph. Chance of precipitation is 30%.

    Low: 66 °F

    Chance
    Showers then
    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 81. North wind around 5 mph becoming calm in the afternoon.

    High: 81 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 67. Southeast wind around 6 mph becoming calm after midnight.

    Low: 67 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Partly sunny, with a high near 81. Calm wind becoming south 5 to 7 mph in the afternoon.

    High: 81 °F

    Partly Sunny

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 72.

    Low: 72 °F

    Mostly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 86.

    High: 86 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms between 8pm and 2am. Partly cloudy, with a low around 73. Chance of precipitation is 40%.

    Low: 73 °F

    Chance
    T-storms

  • Friday

    Friday: Mostly sunny, with a high near 87.

    High: 87 °F

    Mostly Sunny

Detailed Forecast

This Afternoon
A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 81. Southwest wind around 11 mph, with gusts as high as 21 mph.
Tonight
A chance of showers and thunderstorms before 8pm, then a slight chance of showers between 8pm and 11pm. Mostly cloudy, then gradually becoming mostly clear, with a low around 66. North wind 5 to 10 mph. Chance of precipitation is 30%.
Tuesday
Mostly sunny, with a high near 81. North wind around 5 mph becoming calm in the afternoon.
Tuesday Night
Mostly cloudy, with a low around 67. Southeast wind around 6 mph becoming calm after midnight.
Wednesday
Partly sunny, with a high near 81. Calm wind becoming south 5 to 7 mph in the afternoon.
Wednesday Night
Mostly cloudy, with a low around 72.
Thursday
Mostly sunny, with a high near 86.
Thursday Night
A chance of showers and thunderstorms between 8pm and 2am. Partly cloudy, with a low around 73. Chance of precipitation is 40%.
Friday
Mostly sunny, with a high near 87.
Friday Night
Partly cloudy, with a low around 73.
Saturday
A 40 percent chance of showers. Mostly sunny, with a high near 85.
Saturday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 72.
Sunday
Mostly sunny, with a high near 85.
Sunday Night
Partly cloudy, with a low around 72.
Monday
Sunny, with a high near 86.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Stony Brook NY
 40.92°N 73.15°W (Elev. 36 ft)
Last Update:
4:32 pm EDT Aug 3, 2026
Forecast Valid:
5pm EDT Aug 3, 2026-6pm EDT Aug 10, 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