Great Diamond Island Weather Forecast

    • 45
    • 53

    Mostly Cloudy

    • 46
    • 51

    Slight Chance Rain Showers

    • 44
    • 48

    Rain

    • 45
    • 48

    Chance Rain Showers

    • 47
    • 50

    Chance Rain Showers

    • 48
    • 56

    Slight Chance Rain Showers

Today 20 May Coastal Cumberland

Mostly cloudy. Highs in the mid 50s. North Winds around 10 Mph with Gusts up to 25 Mph.

Tonight 20 May Coastal Cumberland

Mostly cloudy in the Evening, then becoming partly cloudy. Lows in the mid 40s. Northeast Winds around 10 Mph with Gusts up to 20 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Great Diamond Island Temperature Statistics

May Temperature

Portland, Portland International Jetport (5 miles)

  • Lowest 1 May, 2025

    36.6 °F

  • Average May

    53.4 °F

  • Highest 8 May, 2025

    68.6 °F

Climate (2020–Present)

Portland, Portland International Jetport (5 miles)

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  • Average Low 2020–2025

    40.7 °F

  • Average 2020–2025

    49.1 °F

  • Average High 2020–2025

    57.5 °F
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