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Why are the Great Lakes so cold?

Lake temperatures are largely driven by interactions with the atmosphere, so colder air temperatures lead to colder lake temperatures, according to the NOAA Great Lakes Environmental Research Laboratory (GLERL).



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Lake Erie and Ontario average the mid to upper 70s by late summer, because of their shallowness. Lake Superior, of course, comes in last with the peak temperatures in the mid-60s. Here in Michigan we are lucky to have four of the five Great Lakes at easy access.

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A north-northeast wind has pushed the warmer surface water along the Michigan shore back toward the middle of Lake Michigan and brought up colder water from well beneath the surface. This process is called upwelling.

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Lake Superior is the world's largest freshwater lake by area (31,700 mi2 /82,100 km2). It is also the coldest and deepest of the Great Lakes, with a maximum depth of 406 meters (1,332 feet).

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The Great Lakes are fascinating and a dream come true for swimmers. Yes, we can all swim in the Great Lakes. It's even possible to swim in all five Great Lakes in less than 24 hours!

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It's the 'forgotten' Great Lake Lake Huron is often overlooked compared with the other four Great Lakes. Superior has a reputation as the coldest, deepest and largest.

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The water in the Great Lakes is owned by the general public according to the Public Trust Doctrine. The Public Trust Doctrine is an international legal theory – it applies in both Canada and the United States, so it applies to the entirety of the Great Lakes.

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Lake Superior is the Cleanest and Clearest Great Lake Because of its somewhat isolated location and long cold winters, not much farming is done along Superior's shores. This means lower amounts of nutrients, sediments, and organic material are floating around the lake.

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When the lake is deep, and the angle of incoming light is smaller, Lake Michigan's color appears deep blue. This is because the light travels down with little obstructions and dissipates far below the surface. The light then appears darker in the visible spectrum.

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Safe for Swimming? The answer is, it depends. Under the right conditions, Lake Michigan is safe for swimming. But this lake can also present dangerous, even deadly, conditions for swimmers.

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Lake Surface Temperature Surface temperatures of Lake Michigan follow a monthly pattern with the warmest temperatures occurring in late summer and early fall and the coolest temperatures occurring in late winter and early spring (Figure 17).

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Lake Michigan in particular is the roughest of the Great Lakes, and poses a major risk to those thinking of taking a dip.

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Lake Superior holds a massive volume of water because of its enormous inland basin and the hundreds of rivers that feed it.

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Climatic conditions control precipitation (and thus groundwater recharge), runoff, and direct supply to the lakes as well as the rate of evaporation. These are the primary driving factors in determining water levels.

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Lake Erie is the fourth-largest lake in North America (by surface area) and the eleventh-largest worldwide. It is the Great Lakes' southernmost, shallowest, and smallest by volume. By the 1960s, Lake Erie had become the most polluted of the Great Lakes, owing to the substantial industrial presence along its coasts.

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Lake Michigan is considered the lake that holds the most deaths among the five Great Lakes in North America. Despite its reputation for powerful undercurrents claiming a minimum of a few lives each year, the warm, welcoming water is a favorite swimming spot for locals and visitors.

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While there have been past “sightings,” most have turned out to be pranks or misidentifications. The reality is that the largest of the Great Lakes (Lake Superior and Michigan) are extremely deep lakes that are too cold for sharks.

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1988: Vicki Keith swims the Great Lakes Vicki Keith's swam Lake Michigan, and was the first person to swim all of the Great Lakes. Some consider her one of the most successful marathon swimmers in the history of the sport with 16 world records.

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Threats & Conservation The source of toxic pollutants includes decades of industrial waste, raw sewage overflows, runoff from cities, and mining operations. Excess nutrients that throw the ecosystem out of balance enter the lakes from agricultural runoff and untreated sewage.

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Lake Superior is safe for swimming. In fact, it has the lowest drowning rate of all the Great Lakes, as reflected in the statistics provided by the Great Lakes Surf Rescue Project. There were 108 confirmed drownings in the Great Lakes in 2022, along with 12 unknown final outcomes.

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At the deepest measured point, Lake Superior is 1,332 feet, around a quarter-mile straight down. Again, comparing it to the next deepest point in another Great Lake, Lake Michigan comes in second with a depth of 925 feet.

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