Woman swimming in the ocean

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Get in the Water
Average ocean water temperatures are highest in August, most notably in the northern Atlantic and Pacific, where frigid readings often keep people on the beach. The water in Bar Harbor, Maine, is as warm as it's going to be all year—as high as a balmy 63—this month. The same goes for Astoria, Oregon, where temps could reach 68. And Lake Superior—the largest, deepest and coldest of the Great Lakes, where the average water temperature in summer is 40 degrees—has climbed all the way to 68 in certain areas this month.