Ancient Cycles of Change
The Great Lakes have never stayed the same. Scientists found cycles stretching back over 4,700 years. During this time, water levels rose and fell through natural climate shifts. For example, Lake Michigan–Huron was once 13 feet higher than today. Then it dropped for centuries before stabilizing at its modern range. These cycles often last 120–200 years, with smaller patterns of 30 years mixed in.
Recorded Highs and Lows
Since 1918, experts have tracked official water levels in all five Great Lakes. Records show huge swings between low and high points. Levels dropped deeply in the 1920s, 1930s, early 1960s, and again in 2013. However, they climbed high in 1929–30, 1952, 1973–74, and the mid-1980s. In fact, 1986 brought some of the highest water ever recorded. More recently, 2020 produced record-breaking highs after a long period of low water.
Weather and Climate Impacts
These dramatic shifts come from rainfall, evaporation, runoff, and ice cover. When winters freeze hard, less water evaporates. But warmer winters reduce ice, so evaporation grows and water levels fall. Heavy rain and storms can push levels up quickly. For example, storms on Lake Erie once raised water by seven feet in Buffalo. Changing climates now make these patterns more extreme and unpredictable across the region.
Recent Trends and Future Outlook
From 1999 to 2013, water stayed unusually low across many lakes. Then, after 2014, levels rose sharply because of wet weather. By 2020, they reached historic highs, causing flooding along shorelines. Yet by 2025, Lake Michigan dropped below its long-term average again. These swings show how the lakes respond to climate and weather together. Looking forward, scientists expect more dramatic highs and lows in coming decades.
