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Great Lakes Current and Historical Water Levels (August 2021 Update)

Updated July 20th. Excepts from the Army Corps of Engineers – Detroit District’s Monthly and Weekly reports for Great Lakes Water Levels and Great Lakes Water Level History.

Estimated reading time: 11 minutes


Great Lakes Basin Weather Conditions Affecting Water Levels

Temperatures in the Great Lakes region were above average for this time of year in mid-August. The week began and ended with wet conditions in the Superior and Michigan-Huron basins. The Michigan-Huron basin has received approximately 1.5 inches of rain the second week of August. Severe storms have caused widespread power outages and flash flooding in areas such as southeast Wisconsin and metro Detroit, Michigan, over the workweek. The rainy weather is expected to end on Friday, and the weather is expected to be dry this weekend. Many cities are expected to have bright and pleasant weather to begin the week, with high temperatures ranging from the high 70s to the low 80s Fahrenheit.

All The Great Lake Water Levels Remain Above Long Term Average

Following a wet week in the second week of August, anticipated water levels on Lakes Michigan-Huron, Erie, and Ontario for Friday, August 13th is 1-4 inches higher than one month ago, while Lake Superior and Lake St. Clair are expected to be near one month ago levels. All of the lakes’ water levels are 6-14 inches lower than last year and remain below record highs. All lakes, with the exception of Lake Ontario, have water levels that are higher than their long-term average August levels. Water levels in the Michigan-Huron, St. Clair, Erie, and Ontario rivers are expected to drop 2-5 inches over the next month. In one month, Lake Superior is expected to continue at its current level.

Lakes Michigan-Huron Water Levels

Lakes Michigan-Huron Water Levels August 2021

On August 13th, the water level is forecasted at 580..97 feet. Lake Michigan-Huron had dropped 14 inches since August 2020, and rising 4 inches over the past month. Levels were down 13 inches below the monthly high record set in 2020. Lake Huron remains at 52 inches above the record monthly low, set in 1964. The lakes are expected to drop by three inches through mid-September 2021. Lake Michigan-Huron is expected to stay above its long-term monthly mean water level for the rest of 2021. For reporting purposes, Lakes Michigan-Huron is the same body of water.

Lake Superior Water Level

Lake Superior Water Level August 2021

As of August 13th, 2021, the Lake Superior water level is forecasted to be 602.23 feet. This is 12 inches less than the high record monthly mean water level set in 2019 and 22 inches higher than the lowest record set in 2007. Over the next month, Lake Superior is expected to remain the same. Lake Superior is expected to stay above its long-term monthly mean water level for the rest of 2021.

Early projects show that due to La Nina weather patterns of the past, Lake Superior may again approach record water levels during the Fall of 2021.

Lake St. Clair Water Level

Lake St. Clair Water Levels August 2021

As of August 13th, 2021, Lake St. Clair’s water level is forecasted to be 576.51 feet. This is 10 inches less than the high record monthly mean water level set in 2020 and 52 inches higher than the lowest record set in 1934. Over the next month, Lake St. Clair is expected to drop by 3 inches through mid-September. Lake St. Clair is expected to stay above its long-term monthly mean water level for the rest of 2021.

Lake Erie Water Level

Lake Erie Water Levels August 2021

As of July 16th, 2021, Lake Erie’s water level is forecasted to be 573.49 feet. This is 9 inches less than the record high water level set in 2019 and 54 inches higher than the lowest record set in 1934. Over the next month, Lake Erie is expected to drop by 5 inches. Lake Erie is expected to stay above its long-term monthly mean water level for the rest of 2021.

Lake Ontario Water Level

Lake Ontario Water Levels August 2021

As of August 13th, Lake Ontario’s water level is forecasted to be 245.6 feet. This is 28 inches less than the record high monthly mean water level set in 1947 and 34 inches higher than the lowest record set in 1934. Over the next month, Lake Ontario is expected to drop by 2 inches. Lake Ontario is expected to fall below its long-term monthly mean water level for the rest of 2021.


July-August Downbound Outflows Expected To Remain Above Average

In August, Lake Superior’s outflow through the St. Marys River is expected to be lower than usual. The discharge of Lake Michigan-Huron through the St. Clair River and the outflow of Lake St. Clair into the Detroit River are expected to be above average in August. In August, Lake Erie’s outflow into the Niagara River is expected to be higher than average, and Lake Ontario’s outflow into the St. Lawrence River is expected to be higher than average.


Water Level Data 1919-2021

Below are the monthly mean average water levels for each of the Great Lakes. All levels are referenced to the International Great Lakes Datum of 1985 (IGLD 85). Water levels have been coordinated with Canada for 1918-2020.

Great Lakes Water Levels 1919-2021
Great Lakes Water Levels 1919-2021

Long Term Great Lakes Water Measurement Experimental Estimates (Last Report July 2021)

Experimental 5-year Outlook of Great Lakes Water Levels by the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory, The four narrow panels to the right depict the range of variability (shown as shaded vertical lines) of monthly mean water levels within the subsequent two to four 12-month periods of the outlook horizon, as well as the annual mean water level predicted for those 12 month periods (shown as large dark points).

In addition to outlook data, graphics include a red horizontal line showing the long term average annual water level (LTA Annual), black bars showing long term average monthly mean water levels (LTA Monthly), and gray bars showing long term maximum and minimum monthly mean water levels (Max/Min Monthly).

Lakes Michigan-Huron Water Levels Experimental 5 Year Forecast

Lakes Michigan-Huron Water Levels Experimental 5 Year Forecast
Lakes Michigan-Huron Water Levels Experimental 5 Year Forecast

The experimental forecast for the next five years shows Lakes Michigan-Huron to remain above the yearly and monthly long-term averages for the next five years.

Lake Superior Water Levels Experimental 5 Year Forecast

Lake Superior Water Levels Experimental 5 Year Forecast
Lake Superior Water Levels Experimental 5 Year Forecast

The experimental forecast for the next five years shows Lake Superior to remain above the yearly long-term average and fluctuate within its monthly long-term averages for the next five years.

Lake St. Clair Water Levels Experimental 5 Year Forecast

Lake St. Clair Water Levels Experimental 5 Year Forecast

The experimental forecast for the next five years shows Lake St. Clair to remain above the yearly and monthly long-term averages for the next five years.

Lake St. Clair Water Levels Experimental 5 Year Forecast

Lake Erie Water Levels Experimental 5 Year Forecast
Lake Erie Water Levels Experimental 5 Year Forecast

The experimental forecast for the next five years shows Lake Erie to remain above the yearly and monthly long-term averages for the next five years.


2020 Was A Record Year for the Great Lakes

These levels made 2020 a record year.

This past August, La Niña conditions developed in the equatorial Pacific Ocean. This means that the sea surface temperatures in the eastern and central equatorial Pacific oceans are cooler than normal.
When this occurs, there can be impacts on the Great Lakes region’s weather, especially in the winter. The current forecast issued by the Climate Prediction Center expects that La Niña will last through the winter. The weather conditions that typically occur then a La Niña is present in the winter. For the Great Lakes basin, southern portions of the basin could experience wetter than normal conditions, and colder air could push further south into the region.

2020 Yearly Great Lakes Water Volume History

Lake Michigan-Huron has set a record high monthly mean level for 9 consecutive months. Also, the August 2020 level was 4 inches above its August 2019 level and 33 inches above its August Long Term Average level.

Dynamic Great Lakes – Lake Level Viewer – From NOAA

Daily Great Lakes Level History

The report below is a view of long-term, basin-scale hydrological data for the Laurentian Great Lakes. Levels are continuously observed by U.S. and Canadian federal agencies in the region through binational cooperation. NOAA-GLERL relies on this water level data to conduct research on the regional water budget components and improve predictive models.

NOAA’s Center operates water level monitoring stations for Operational Oceanographic Products and Services and the Department of Fisheries and Oceans’ Canadian Hydrographic Service. The U.S. Army Corps of Engineers (Detroit, Chicago, Buffalo) and Environment and Climate Change Canada play crucial roles in research, coordination of data, and operational seasonal water level forecasts for the basin.

Observed Lake Huron Levels at Harbor Beach, Michigan

Current Weather and Lake Huron Conditions at Harbor Beach Michigan

Key Questions on Great Lakes Levels

Are Great Lakes water levels climbing or receding?

All the Great Lake water levels remain above their long-term average. Except for Lake Superior, all the Great Lakes are expected to remain above their long-term averages for the next five years.

Why are Great Lakes water levels staying so high?

Water levels follow a seasonal cycle where water levels rise in the spring due to increased precipitation and enhanced runoff from snowmelt. In the fall, the lakes generally decline due to an increase in evaporation as temperatures decline and cold air moves over the relatively warm lake waters. However, the high rates of precipitation in the Upper Great Lakes have kept overall lake levels high

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