Your real-time guide to the UP
Live weather, road conditions, northern lights forecasts, and local insights — everything you need before you head out.
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Lake Superior is the deepest and coldest of the Great Lakes, and it warms slowly. Open water often sits in the 40s and low 50s°F even at the height of summer, while shallow, sheltered bays — Munising Bay, Au Train Bay and Keweenaw Bay among them — can climb into the 60s after a run of warm, calm days. The water temperature on the cards above is read from the nearest NOAA buoy or shore gauge, so treat it as the temperature of the open lake near that point rather than the temperature at any one beach.
Cold water shock is the real hazard on Lake Superior, not depth or distance. Sudden immersion below roughly 60°F triggers an involuntary gasp and rapid breathing that can overwhelm a strong swimmer inside the first minute. Air temperature is a poor guide — an 80°F afternoon on a Marquette beach can sit over water in the low 50s. Check the reading, wade in slowly, and stay within your depth.
Superior’s fetch, the open distance wind can travel across it, is long enough that a steady blow builds waves quickly, and the lake is roughest from September through November when autumn gales cross it. The wave height above is measured offshore at the buoy; the nearshore break and rip currents along beaches like McCarty’s Cove, Grand Marais and Whitefish Point can be very different, and the National Weather Service issues beach hazard statements separately.
Level is reported in feet above the IGLD 1985 datum, the standard reference surface for the Great Lakes. Lake Superior’s long-term mean is 600.7 ft, so the “vs long-term mean” figure shows how the lake compares with its century-scale average — a practical signal for how wide the beaches are running, how much water is under a boat launch, and how much shoreline you will actually find when you get there.