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

63°F

17°C

Humidity 52%
Wind Speed NE 13 mph
Barometer 30.14 in (1020.7 mb)
Dewpoint 45°F (7°C)
Visibility 10.00 mi
Last update 19 Sep 5:56 am EDT
Extended Forecast for

Great River NY

  • Today

    Today: Partly sunny, with a high near 69. Northeast wind 11 to 14 mph.

    High: 69 °F

    Partly Sunny

  • Tonight

    Tonight: Mostly cloudy, with a low around 59. Southeast wind 8 to 10 mph.

    Low: 59 °F

    Mostly Cloudy

  • Sunday

    Sunday: Rain likely, with thunderstorms also possible after 5pm. Mostly cloudy, with a high near 71. Southeast wind 10 to 14 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    High: 71 °F

    Chance Rain
    then Rain
    Likely

  • Sunday Night

    Sunday Night: Rain and possibly a thunderstorm. Low around 59. South wind 8 to 11 mph becoming north after midnight. Chance of precipitation is 90%. New precipitation amounts between three quarters and one inch possible.

    Low: 59 °F

    Rain

  • Monday

    Monday: A 30 percent chance of rain, mainly before 8am. Mostly cloudy, with a high near 67. Breezy, with a northeast wind 15 to 20 mph.

    High: 67 °F

    Chance Rain
    and Breezy

  • Monday Night

    Monday Night: Mostly cloudy, with a low around 57.

    Low: 57 °F

    Mostly Cloudy

  • Tuesday

    Tuesday: A 30 percent chance of showers after 2pm. Mostly cloudy, with a high near 64. Breezy.

    High: 64 °F

    Breezy.
    Mostly Cloudy
    then Chance
    Showers

  • Tuesday Night

    Tuesday Night: A 30 percent chance of showers before 8pm. Mostly cloudy, with a low around 56. Breezy.

    Low: 56 °F

    Breezy.
    Chance
    Showers then
    Mostly Cloudy

  • Wednesday

    Wednesday: Mostly cloudy, with a high near 65. Windy.

    High: 65 °F

    Mostly Cloudy
    and Windy

Detailed Forecast

Today
Partly sunny, with a high near 69. Northeast wind 11 to 14 mph.
Tonight
Mostly cloudy, with a low around 59. Southeast wind 8 to 10 mph.
Sunday
Rain likely, with thunderstorms also possible after 5pm. Mostly cloudy, with a high near 71. Southeast wind 10 to 14 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Sunday Night
Rain and possibly a thunderstorm. Low around 59. South wind 8 to 11 mph becoming north after midnight. Chance of precipitation is 90%. New precipitation amounts between three quarters and one inch possible.
Monday
A 30 percent chance of rain, mainly before 8am. Mostly cloudy, with a high near 67. Breezy, with a northeast wind 15 to 20 mph.
Monday Night
Mostly cloudy, with a low around 57.
Tuesday
A 30 percent chance of showers after 2pm. Mostly cloudy, with a high near 64. Breezy.
Tuesday Night
A 30 percent chance of showers before 8pm. Mostly cloudy, with a low around 56. Breezy.
Wednesday
Mostly cloudy, with a high near 65. Windy.
Wednesday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 56. Windy.
Thursday
A 40 percent chance of showers. Mostly cloudy, with a high near 64. Windy.
Thursday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 55. Windy.
Friday
A 40 percent chance of showers. Mostly cloudy, with a high near 65. Windy.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Great River NY
 40.7°N 73.17°W (Elev. 7 ft)
Last Update:
3:16 am EDT Sep 19, 2026
Forecast Valid:
6am EDT Sep 19, 2026-6pm EDT Sep 25, 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