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Where Lake Michigan–Huron stands today against chart datum, the month's long-term average and the records — from NOAA's gauge and a century of published measurements, with the six-month outlook.
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19 in (49 cm) above chart datum
4 in (10 cm) below the August average since 1918
On an island, the lake's level is the shoreline: the docks, the marina, the beaches, and M-185 — the car-free road around the island that the 2019–2020 high water ate into the lake. Lake Michigan and Lake Huron are one lake hydraulically, joined right here at the Straits, so they rise and fall together; this page shows where that lake stands today against the century of measurements behind it.
Gauge reading · the gauge is NOAA's Mackinaw City station, across the Straits from the island — on a lake this size the level story is the same on both shores.
NOAA and the Army Corps’ coordinated forecast puts Lake Michigan–Huron between 22 in (57 cm) and 25 in (63 cm) above chart datum around its August peak.
A forecast band, updated monthly — where the seasonal rise and fall is expected to land, not a promise.
Computed from the published lakewide monthly averages for Lake Michigan–Huron, 109 years of them.
When the lake pushed toward its record in 2019 and 2020, waves ate roughly four miles of M-185 between British Landing and Arch Rock — the only state highway in America where cars are banned — and MDOT spent nearly $6 million rebuilding it in 2021. The Mackinaw City gauge recorded its highest instantaneous reading ever, 582.8 ft, on 19 July 2020.
Source: UpNorthLive / MDOT, repair completed October 2021; record reading per NOAA station datums, checked July 2, 2026 (last month).
The other extreme is just as local: in January 2013 the lake set its record LOW monthly average after two mild, dry winters — the years harbors across northern Lake Huron were talking about dredging and long walks to the waterline. The lake has swung nearly two metres between its recorded extremes; both ends of that swing have reshaped this shoreline within living memory.
Source: NOAA GLERL lakewide monthly series, 1918–present, checked July 2, 2026 (last month).
Lake Michigan and Lake Huron are connected at the Straits of Mackinac by a channel wide and deep enough that they hold one common surface — hydrologically one lake, the largest by surface area on Earth. That is why the official statistics treat them together, and why what happens to the level here happens from Chicago to Georgian Bay.
Source: NOAA Great Lakes Environmental Research Laboratory, checked July 2, 2026 (last month).
A lake level is not a wave height and not a storm surge — wind can pile water well up a shore in hours, and a calm number here says nothing about conditions on the water or at the shoreline today.
Chart datum — the Low Water Datum — is the fixed reference nautical charts use for Lake Michigan–Huron: 577.5 ft (176.0 m). "Two feet above datum" means two feet more water than the charts assume — which is what a dock, a breakwall or a shoreline path actually feels.
The “right now” reading is preliminary until NOAA verifies it, and it is one gauge, not the whole lake; the averages and records describe the lake as a whole.
Data: NOAA CO-OPS and NOAA GLERL (Great Lakes water level dashboard), with the USACE Detroit District monthly bulletin — US government works, public domain.