Average Ocean Temperatures for Maine & New Hampshire

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Average ocean temperatures for Maine and New Hampshire are listed below for each month in degrees Fahrenheit and degrees Celsius.

During winter, the sea temperatures off northern New England are similar to those all along the coast as far south as Maryland. But come spring and summer, the ocean off of Maine simply doesn't build up much heat. The Atlantic ocean all along the coast of Maine and New Hampshire is noticeably chillier in summer than at beaches farther south.

At the north end of the US Atlantic coast, the ocean at Eastport Maine usually reaches 52 °F (11 °C) in late summer. But just a little to the southeast, at Bar Harbor, next to Acadia National Park, the ocean gets several degrees warmer.

Maine's waters are too cold for most people to stay in for long. Only the hardiest of swimmers can spend much time in the ocean off northern New England without a wetsuit.

Average ocean temperature in °F
  Portsmouth
NH
Portland
ME
Bar Harbor
ME
Eastport
ME
January 40 34 38 40
February 35 33 36 37
March 37 37 38 38
April 43 40 44 40
May 50 49 49 44
June 55 56 55 46
July 60 61 59 51
August 62 62 62 51
September 59 59 58 52
October 52 52 54 50
November 48 47 52 45
December 41 39 44 45
Annual 48 47 49 45
Water temperature averages in °C
  Portsmouth
NH
Portland
ME
Bar Harbor
ME
Eastport
ME
January   4   1   3   4
February   2   1   2   3
March   3   3   3   3
April   6   4   6   4
May 10   9   9   6
June 13 13 13   8
July 16 16 15 10
August 16 16 16 11
September 15 15 14 11
October 11 11 12 10
November   9   8 11   7
December   5   4   7   7
Annual   9   8   9   7

These coastal water temperatures are averages compiled by the National Oceanographic Data Center. Actual ocean temperatures do vary from year to year depending upon the weather and the flow of ocean currents.

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