Straight from the Tap

Lake Erie is Ready to Freeze


Since the start of 2019, the temperature of the lake water coming into Cleveland Water’s Garrett Morgan Treatment Plant has stayed below 39.2°F (4°C). This is the magic number that signals the lake’s surface can now start to freeze.

Water’s density is highest at a temperature of 39.2°F. Any colder than that and water becomes less dense at it approaches its solid state of ice. Any warmer and it also loses density.

In summer, the lake water separates into distinct layers based on water density differences caused by temperature variations. Colder, denser water sinks to the bottom and warmer, lighter water stays at the top.

In winter, it’s different.

Once Lake Erie’s bottom waters reach and maintain temperatures below 39.2° F, the surface water will continue to cool if the air temperatures are colder than the water. Further cooling to temperatures lower than 39.2° F makes the surface water less dense and lighter, so it will float on top of the warmer but denser water below it and continue to cool. And if air temperatures stay below 32°F, ice will begin to form.

In typical Januarys, water temperatures at the bottom of the lake will be just above the freezing point. Ice cover data for the Great Lakes is tracked by the National Oceanic and Atmospheric Administrations’ Great Lakes Environmental Research Laboratory (NOAA GLERL) and available on their website. Based on their historical data from 1973-2018, the average ice cover for Lake Erie for January 10 is 33%.

So far the winter of 2018-2019 is neither typical nor average. We’ve had several days of temperatures in the 40s and 50s and precipitation has mostly been in the form of rain instead of snow. We’ve even had thunderstorms and tornados touching down in Ohio in January. Ice and cold air have been in short supply until recently. But we all know how unpredictable Cleveland weather is! So we'll continue watching Lake Erie's ice cover along with the other parameters we regularly monitor.





1/15/2019 36.1 2.3
1/14/2019 36.4 2.4
1/13/2019 38.8 3.9
1/12/2019 37.1 2.8
1/11/2019 37.2 2.9
1/10/2019 37.9 3.3
1/9/2019 38.3 3.5
1/8/2019 38.4 3.6
1/7/2019 38.3 3.5
1/6/2019 38.1 3.4
1/5/2019 38 3.3
1/4/2019 38.2 3.4
1/3/2019 38.5 3.6
1/2/2019 38.7 3.7
1/1/2019 38.8 3.8