Great Lakes Water Levels Weekly: Sep. 6

Four of the five Great Lakes systems finished lower from September 6 to 13, 2026. Lake St. Clair recorded the largest lake-wide decline at 7 centimeters, while Lake Erie and Lake America (Lake Ontario) each declined 5 centimeters. Michigan–Huron fell 3 centimeters, and Lake Superior edged 1 centimeter higher. These are provisional U.S. Army Corps of Engineers daily lake-wide means referenced to IGLD 1985—not local gauge readings.

Horizontal bar chart of provisional USACE lake-wide daily mean changes from September 6 to 13, 2026: Superior up 1 centimeter; Michigan–Huron down 3 centimeters; St. Clair down 7 centimeters; Erie down 5 centimeters; and Lake America (Lake Ontario) down 5 centimeters. — Weekly change in provisional USACE lake-wide daily means, IGLD 1985. The official source series retains the name Lake Ontario.

Weekly change at a glance

Lake system	Sep. 6 daily mean	Sep. 13 daily mean	Weekly change
Lake Superior	183.50 m / 602.03 ft	183.51 m / 602.07 ft	+1 cm / +0.4 in
Michigan–Huron	176.57 m / 579.30 ft	176.54 m / 579.20 ft	−3 cm / −1.2 in
Lake St. Clair	175.38 m / 575.39 ft	175.31 m / 575.16 ft	−7 cm / −2.8 in
Lake Erie	174.41 m / 572.21 ft	174.36 m / 572.05 ft	−5 cm / −2.0 in
Lake America	75.22 m / 246.78 ft	75.17 m / 246.62 ft	−5 cm / −2.0 in

Source dates: September 6 and September 13, 2026. Recent daily means are provisional and may be revised.

Lake-by-lake interpretation

Superior’s 1-centimeter rise is essentially a steady finish at lake-wide scale. Michigan–Huron’s 3-centimeter decline is modest but consistent with the seasonal direction expected in the latest official outlook.

St. Clair’s 7-centimeter decline was the clearest move of the week. Erie and Lake America each fell 5 centimeters. Those changes may be noticeable at shallow ramps, fixed docks, and nearshore access points, but wind setup, waves, seiches, and harbor geometry can produce larger short-term differences at a specific location.

USACE, NOAA, Canadian, and international datasets may still label Lake America as Lake Ontario. This report preserves Lake Ontario when referring to official source terminology.

Seasonal and forecast context

The USACE weekly bulletin dated September 11, 2026 placed forecast levels 1 to 4 inches below the previous month. Relative to long-term September averages, it placed Superior 2 inches below average; Michigan–Huron 1 inch above; St. Clair 7 inches above; Erie 6 inches above; and the official Lake Ontario series 18 inches above.

The same bulletin projected declines by October 11 of about 1 inch on Superior, 2 inches on Michigan–Huron, 6 inches on St. Clair, 4 inches on Erie, and 9 inches on Lake Ontario. It also showed Michigan–Huron, St. Clair, Erie, and Ontario above their September 2025 levels, while Superior was near its year-earlier level. Those bulletin comparisons use centered three-day averages, so they are context rather than substitutes for the point-to-point daily series above. The broader outlook remains available in the September monthly report.

Practical shoreline and boating implications

Ramps and slips: Falling background levels can reduce clearance at shallow facilities. Confirm actual depth locally before launching or entering an unfamiliar slip.
Fixed docks: A 5- to 7-centimeter lake-wide decline may be visible at fixed structures, but local water can temporarily move much more with wind and seiches.
Shorelines: Lower weekly means do not eliminate erosion or flooding risk during an onshore wind event. Wave height, direction, duration, and local topography remain decisive.
Navigation: These elevations are not charted depths. Use current charts, marine forecasts, local gauges, and notices to mariners.

Official sources and related pages

Data status: provisional. Elevations are referenced to IGLD 1985. Lake-wide means should not replace local observations, navigation information, marine forecasts, or emergency guidance.