Most of the watershed that feeds the lake is located in Vermont, and is a source for accumulated phosphorus, sediments, and other pollutants.

In Quebec, the lake lies in parts of Austin, Magog, Ogden, Potton, Saint-Benoît-du-Lac, and Stanstead Township, all in Memphrémagog Regional County Municipality.

Its maximum recorded depth of 351 feet (107 m) is located in Canada, opposite Jewett Point (at approximately 45°06′42″N 72°16′43″W / 45.111621°N 72.278491°W / 45.111621; -72.278491).

[11] The lake is irregular in shape, and along its shores are several striking indentations, in some places low, and in some other parts high and rocky.

[12] Along the western shore of the lake are several mountains, prominent among which are Owl's Head, Elephantis, and the Hog's Back.

The hydroelectric producing Memphemagog Dam, on the Magog River, regulates the water level of the lake.

[15]: 121 Like many other lakes, Memphremagog is accumulating phosphorus, sediments, and other pollutants, primarily runoff from farms, but from other sources as well.

[24] In June 1942, a single-engined Royal Canadian Air Force training plane crashed into the lake near the west shore near Newport, killing the pilot, Roy N. Pate, its only occupant.

Fish and Wildlife Service accepted a bequest of 420 acres (170 ha) of undeveloped land on the shores the lake on Eagle Point along the border with Canada.

[27] In September 2020, a leak at the sewage treatment facility in Newport, Vermont dumped about 7,000 gallons of effluent into the lake.

[28] Lake Memphremagog allegedly contains a cryptid named Memphre (or Memphré), which has received sightings since the 18th century and continues on in the folklore of the area.

The Maxfield Point Light was a small lighthouse constructed on the Vermont side of Lake Memphremagog in 1879.

The lighthouse was a steel skeleton tower, painted red, that was fixed on a concrete foundation.

The tower showed a fixed red light that was visible for up to 12 mi (19 km), with the height of the focal plane being 37 feet (11.2 m).

It had a fixed white dioptric light located at a height of 19 feet (5.8 m) above the high water mark and with a range of 9 miles (14 km).

It had a fixed white catoptric light located at a height of 24 feet (7.3 m) above the high water mark and with a range of 8 miles (13 km).

In 1980, that was replaced by a modern 22 feet (6.7 m) steel tower with a fixed white light that has a range of 8 miles (13 km).

[40] Château de Silva Lighthouse was located on the western side of the lake at the Revere House (formerly the Château de Silva) hotel wharf, approximately 5 miles (8.0 km) southwest of the Wadleigh's Point lighthouse.

[5] In 2011, a day cruise ship started summer operations on the Canadian side of the lake.

[45] 2021 data for water quality, aquatic invasive species, and cyanobacteria reveal that Lake Memphremagog is still impaired, but trends are stabilizing.

It was started in 1935 by several families in the bay, with the goal of teaching their children the basics of the sport they all cherished so much, sailing.

Lake Memphremagog is mentioned in Northwest Passage, a historical novel by Kenneth Roberts about the 1759 Rogers' Rangers raid.

In Northwest Passage, the 1940 film based on the novel, Spencer Tracy uses a map that shows Lake Memphremagog and the environs.

[47] The Canadian band The Tragically Hip mentions Lake Memphremagog in their 2002 unreleased song "Problem Bears", part of their In Violet Light album sessions.

Lake Memphremagog was mentioned and depicted in Disappearances, a 2006 film by director Jay Craven starring Kris Kristofferson, and co-starring Charlie McDermott and Geneviève Bujold.

Lake Memphremagog was the setting for the climactic scene in Kenneth Butler's satiric novel Holy Fool (TouchPoint Press, 2015).