Your Ultimate Boating Resource

HomeForecastsMaine ForecastsGreat Diamond Island, ME Marine Weather

Great Diamond Island, ME Marine Weather Forecast

Station CASM1 - 8418150 - Portland, ME

December 29, 2025 6:48 pm EST
Location: 43.656N 70.246W
Wind Direction: W (260°)
Wind Speed: 7.0 knots
Wind Gust: 9.9 knots
Atmospheric Pressure: 29.09 in (985.0 mb)


Tonight - 21°F
Dec 29, 2025
15 to 30 mph W
Freezing Rain then Mostly Cloudy
Freezing rain and areas of fog before 8pm. Mostly cloudy, with a low around 21. West wind 15 to 30 mph, with gusts as high as 40 mph. Chance of precipitation is 70%. New rainfall amounts less than a tenth of an inch possible.
Tuesday - 25°F
Dec 30, 2025
25 to 30 mph W
Partly Sunny
Partly sunny, with a high near 25. West wind 25 to 30 mph, with gusts as high as 40 mph.
Tuesday Night - 18°F
Dec 30, 2025
25 to 30 mph W
Partly Cloudy
Partly cloudy, with a low around 18. West wind 25 to 30 mph, with gusts as high as 40 mph.
Wednesday - 32°F
Dec 31, 2025
15 to 25 mph W
Mostly Cloudy then Slight Chance Light Snow
A slight chance of snow after 3pm. Mostly cloudy, with a high near 32. West wind 15 to 25 mph, with gusts as high as 35 mph.
Wednesday Night - 20°F
Dec 31, 2025
15 mph W
Slight Chance Light Snow then Chance Snow Showers
A slight chance of snow before 7pm, then a chance of snow showers. Mostly cloudy, with a low around 20. West wind around 15 mph, with gusts as high as 25 mph. Chance of precipitation is 50%. New snow accumulation of less than one inch possible.
New Year's Day - 25°F
Jan 01, 2026
15 mph NW
Chance Snow Showers then Mostly Sunny
A chance of snow showers before 11am. Mostly sunny, with a high near 25. Chance of precipitation is 40%. New snow accumulation of around one inch possible.
Thursday Night - 14°F
Jan 01, 2026
15 mph W
Mostly Clear
Mostly clear, with a low around 14.
Friday - 25°F
Jan 02, 2026
15 mph W
Mostly Sunny
Mostly sunny, with a high near 25.
Friday Night - 20°F
Jan 02, 2026
15 mph W
Partly Cloudy
Partly cloudy, with a low around 20.
Saturday - 28°F
Jan 03, 2026
10 to 15 mph W
Mostly Sunny
Mostly sunny, with a high near 28.
Saturday Night - 16°F
Jan 03, 2026
10 mph NW
Partly Cloudy
Partly cloudy, with a low around 16.
Sunday - 24°F
Jan 04, 2026
10 mph NW
Slight Chance Snow Showers
A slight chance of snow showers. Mostly sunny, with a high near 24.
Sunday Night - 16°F
Jan 04, 2026
10 mph NW
Slight Chance Snow Showers
A slight chance of snow showers before 1am. Mostly cloudy, with a low around 16.
Monday - 28°F
Jan 05, 2026
10 to 15 mph W
Mostly Cloudy then Slight Chance Snow Showers
A slight chance of snow showers after noon. Mostly cloudy, with a high near 28.

Don't Miss