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.

Partly Cloudy

70°F

21°C

Humidity 97%
Wind Speed Calm
Barometer 29.85 in (1010.7 mb)
Dewpoint 69°F (21°C)
Visibility 10.00 mi
Last update 18 Aug 12:56 am EDT
Extended Forecast for

Smithtown NY

  • Overnight

    Overnight: Patchy fog after 2am. Otherwise, mostly cloudy, with a low around 69. Calm wind.

    Low: 69 °F

    Patchy Fog

  • Tuesday

    Tuesday: Patchy fog before 8am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 85. North wind around 6 mph.

    High: 85 °F

    Patchy Fog
    then Mostly
    Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 68. Light northwest wind.

    Low: 68 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 87. Calm wind becoming southwest 5 to 8 mph in the afternoon.

    High: 87 °F

    Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 70. South wind 5 to 8 mph.

    Low: 70 °F

    Partly Cloudy

  • Thursday

    Thursday: A 50 percent chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 84.

    High: 84 °F

    Mostly Sunny
    then Chance
    T-storms

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 66. Chance of precipitation is 50%.

    Low: 66 °F

    Chance
    T-storms then
    Chance
    Showers

  • Friday

    Friday: A 40 percent chance of showers before 2pm. Partly sunny, with a high near 82.

    High: 82 °F

    Chance
    Showers

  • Friday Night

    Friday Night: A 40 percent chance of showers after 8pm. Mostly cloudy, with a low around 65.

    Low: 65 °F

    Chance
    Showers

Detailed Forecast

Overnight
Patchy fog after 2am. Otherwise, mostly cloudy, with a low around 69. Calm wind.
Tuesday
Patchy fog before 8am. Otherwise, mostly cloudy, then gradually becoming sunny, with a high near 85. North wind around 6 mph.
Tuesday Night
Mostly clear, with a low around 68. Light northwest wind.
Wednesday
Sunny, with a high near 87. Calm wind becoming southwest 5 to 8 mph in the afternoon.
Wednesday Night
Partly cloudy, with a low around 70. South wind 5 to 8 mph.
Thursday
A 50 percent chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 84.
Thursday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 66. Chance of precipitation is 50%.
Friday
A 40 percent chance of showers before 2pm. Partly sunny, with a high near 82.
Friday Night
A 40 percent chance of showers after 8pm. Mostly cloudy, with a low around 65.
Saturday
A 40 percent chance of showers. Partly sunny, with a high near 80.
Saturday Night
Showers likely. Mostly cloudy, with a low around 66. Chance of precipitation is 60%.
Sunday
Showers likely. Mostly cloudy, with a high near 81. Chance of precipitation is 60%.
Sunday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 65.
Monday
Mostly sunny, with a high near 82.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Smithtown NY
 40.86°N 73.22°W (Elev. 82 ft)
Last Update:
4:44 pm EDT Aug 17, 2026
Forecast Valid:
1am EDT Aug 18, 2026-6pm EDT Aug 24, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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