ARMY CORPS OF ENGINEERS WEEKLY GREAT LAKES WATER LEVEL UPDATE

Sep 29, 2023

WEATHER CONDITIONS

The Great Lakes region experienced near average temperatures from last Friday to Wednesday this week. A few exceptions to this were Sault Ste Marie, MI. and Marquette, MI. where temperatures were above average. With one day left in the month, the Great Lakes basin has received only 49% of average precipitation for September. Isolated locations did receive considerable precipitation over the past seven days with total accumulation near 6 inches in Duluth, MN and about 3 inches around Milwaukee, WI. Heading into the weekend and beginning of next week, temperatures are forecast to rise to much above average conditions with daily highs from 70 to 80 degrees Fahrenheit. Partly cloudy to sunny conditions are expected across most of the basin over the weekend with minimal precipitation over the coming week. The western half of Lake Superior basin can expect rain Friday and Saturday.

LAKE LEVEL CONDITIONS

Projected September 29^th water levels for Lakes Superior, Michigan-Huron, and Erie are 2 to 5 inches below their levels of a month ago. Also, Lakes St. Clair and Ontario are 7 and 9 inches, respectively, below their levels at this time last month. Water levels forecasted for September 29^th on Lakes Superior and Michigan-Huron are 2 inches below their levels at this time last year. Meanwhile, Lakes St. Clair, Erie, and Ontario’s levels are 1, 3, and 11 inches, respectively, above levels of a year ago. All lakes are still above their long-term September average levels. Over the next 30 days, the forecast shows Lakes Superior and Michigan-Huron declining 2 to 3 inches, while Lakes St. Clair, Erie, and Ontario may drop 6 to 7 inches. See our Daily Levels web page for more water level information.

FORECASTED MONTHLY OUTFLOWS/CHANNEL CONDITIONS

Lake Superior’s outflow into the St. Marys River and Lake Michigan-Huron’s outflow into the St. Clair River are projected to be above average for September. Lake St. Clair outflow through the Detroit River, Lake Erie outflow through the Niagara River, and Lake Ontario outflow through the St. Lawrence River are projected to be above average in September as well.

ALERTS

Water levels shown are still-water surface elevations over the entire lake surface. Water levels at specific locations may differ due to meteorological influences. Official records are based on monthly average water levels and not daily water levels. Great Lakes, connecting channels, and St. Lawrence River users should keep informed of current conditions before undertaking any activities affected by changing water levels. Mariners should use navigation charts and refer to current water level readings. Find ice information at National Ice Center’s website.

SUPERIOR

MICH-HURON

ST. CLAIR

ERIE

ONTARIO

Forecasted Water Level for Sep 29, 2023 (feet)

602.40

579.40

575.46

572.51

245.34

Chart Datum (feet)

601.10

577.50

572.30

569.20

243.30

Difference from chart datum (inches)

+16

+23

+38

+40

+24

Difference from average water level for Aug 29, 2023 (inches*)

-2

-4

-7

-5

-9

Difference from average water level for Sep 29, 2022 (inches*)

-2

-2

+1

+3

+11

Difference from long-term monthly average of Sep (inches)

+3

+3

+11

+12

+2

Difference from highest monthly average of record for Sep (inches)

-10

-31

-19

-15

-25

Year of highest recorded monthly mean

2019

1986

2020

2019

1947

Difference from lowest monthly average of record for Sep (inches)

+23

+33

+42

+44

+34

Year of lowest recorded monthly mean

2007

1964

1934

1934

1934

Projected net change in levels by Oct 29, 2023 (inches)

-2

-3

-7

-6

-7

ALL DATA SHOWN IN THIS SUMMARY ARE REFERENCED TO IGLD 1985

*VALUES FOR SPECIFIC DAY ARE BASED ON 3-DAY DAILY AVERAGE AROUND SPECIFIED DATE

LONG TERM AVERAGE PERIOD OF RECORD, 1918-2022

FORECASTED INFORMATION PROVIDED BY

RECORDED DATA (1918 – present)

FOR MORE INFORMATION VISIT

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