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Northeast Kingdom Area Information

Water Temperature

Some of you have been asking about the water temperatures in this cold water, glacially carved lake in Northern, Vermont. At the end of July, surface temperatures are likely to range between 68 degrees and 75 degrees Fahrenheit in the top three meters of the surface. But don’t swim down near the bottom (351 feet at its deepest) where it stays about 44 degrees Fahrenheit all summer long!

One description of Lake Memphremagog: “It is a lake of exceptional, rugged beauty; set in a diverse landscape, hilly and mountainous to the west, but with pastoral, rolling farmland to the east.” Some of you may remember the 1940 movie, Northwest Passage, starring Spencer Tracy and describing Rogers’ Rangers during the French Indian War and their raid on the Abenaki village of St. Francis. On their return, they camped on the shores of Lake Memphremagog and then split up in order to avoid the counter attack.

When it comes to our lake’s temperatures, there are three distinct environments. At its deepest Lake Memphremagog stays cold. Lower than about 10 feet of the surface, it starts getting very cold, very fast. A significant thermocline exists at about 30 feet below the surface. However, there are three rivers that feed the Lake from the south, the Clyde, the Barton, and the Black. This water tends to be warmer in the summer and the current rides the upper level of the lake like a gulf stream of relatively warmer water. A.T. Drummond, Lake Memphremagog a Cold Water Lake (1893). That’s where the temperatures tend to range between 68 degrees and 75 degrees Fahrenheit this time of year. Then there is the shallower, east side of the lake, which tends to warm up into the 80’s during July and August.

One local reports: “I think it is quite comfortable even in the broad lake at that time of year, especially for someone expending that much effort. I did two mile swims with and without wetsuits and found it too warm with.”

All of this can change if there is a lot of rain, or a lot of wind during the week or two prior to the Swim. Our lake can get pretty stirred up at times. (Which is why we run swimmers up and back along the western side of the lake, sheltered from the prevailing west winds) That can cool things down some. On the other hand, for some stretches of the summer, generally this time of July, the lake can settle down and warm up, at least in the top three meters of the surface.

Most of the 10 mile open water swim will be within the “gulf stream” along the western side of the lake. There is a section of the swim returning on the eastern side of Cove Island, Black Island and Belle Island which will bring you into the relatively shallower, warmer part of the Lake. However, you will soon return to the west for your return to Newport.

The Abenaki were the earliest known settlers of this lake, giving it the name “Memphremagog,” which means “a big expanse of water". It is truly the Northeast Kingdom’s “Great Lake.” When summer’s here, there’s nothing better than to dive in, and swim!!!