Great South Bay Weather Forecast

    • 71
    • 76

    Chance Rain Showers

    • 63
    • 77

    Partly Sunny

    • 64
    • 68

    Mostly Cloudy

    • 64
    • 71

    Rain Showers Likely

    • 63
    • 69

    Chance Rain Showers

    • 62
    • 68

    Chance Rain Showers

Today 17 Sep Southwest Suffolk

Partly sunny this Morning, then becoming mostly cloudy. Highs in the upper 70s. Southwest Winds 10 to 15 Mph.

Tonight 17 Sep Southwest Suffolk

Mostly cloudy. A slight chance of Showers in the Evening, then a chance of Showers after midnight. Humid with Lows in the upper 60s. Southwest Winds 10 to 15 Mph. Chance of rain 40 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Great South Bay Temperature Statistics

September Temperature

Islip, Long Island Mac Arthur Airport (8.1 miles)

  • Lowest 7 September, 2026

    56.6 °F

  • Average September

    72.1 °F

  • Highest 10 September, 2026

    86.6 °F

Climate (2021–2026)

Islip, Long Island Mac Arthur Airport (8.1 miles)

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  • Average Low 2021–2026

    47.2 °F

  • Average 2021–2026

    55.2 °F

  • Average High 2021–2026

    63.1 °F
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