Great Diamond Island Weather Forecast

    • 63
    • 65

    Mostly Sunny

    • 68
    • 72

    Mostly Sunny

    • 64
    • 78

    Rain Showers Likely

    • 62
    • 73

    Partly Sunny

    • 62
    • 70

    Chance Rain Showers

    • 63
    • 73

    Partly Sunny

    • 65
    • 74

    Slight Chance Thunderstorms

Today 23 Jul Coastal Cumberland

Mostly sunny. Highs in the upper 70s. Light and variable Winds, becoming south around 10 Mph with Gusts up to 20 Mph this afternoon.

Tonight 23 Jul Coastal Cumberland

Partly cloudy. Lows in the lower 60s. South Winds around 10 Mph with Gusts up to 20 Mph this Evening, becoming light and variable.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Great Diamond Island Temperature Statistics

July Temperature

Portland, Portland International Jetport (5 miles)

  • Lowest 5 July, 2025

    54.6 °F

  • Average July

    71.8 °F

  • Highest 6 July, 2025

    92.6 °F

Climate (2020–Present)

Portland, Portland International Jetport (5 miles)

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  • Average Low 2020–2025

    40.6 °F

  • Average 2020–2025

    49.1 °F

  • Average High 2020–2025

    57.4 °F
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