Extreme Cold Triggers Rare Pancake Ice Formation on Lake Michigan

A rare meteorological event occurred on Lake Michigan on Monday, December 15, 2025, when an intense cold snap gripping the Upper Midwest led to the documented formation of pancake ice near the North Pier Lighthouse. This striking phenomenon, characterized by circular, disc-like ice chunks, results directly from turbulent, sub-freezing water conditions where active wave action coincides with temperatures significantly below the freezing point.

The mechanics behind this natural spectacle involve wave action disturbing a thin layer of surface ice or slush, causing the resulting fragments to rotate and collide. As these pieces repeatedly strike one another, their edges become rounded, creating the characteristic disc shape. These ice discs can reach diameters up to three meters, often featuring raised rims formed as slush or frazil ice piles up on the edges during continuous collisions. In conditions of strong wave energy, these pancakes can raft over one another, leading to uneven surfaces before eventually fusing into larger ice floes.

Observations of pancake ice on Lake Michigan are not unprecedented during severe cold weather, though they remain a relatively rare occurrence compared to the lake's typical ice cover. Historically, ice cover on the Great Lakes shows high year-to-year variability, with long-term records since 1973 indicating a general trend toward fewer frozen days across the basin. For instance, the area-weighted average for all five Great Lakes shows a 25% decrease in ice cover between 1973 and 2023. The Great Lakes region has experienced some of the strongest winter warming trends in the nation since 1970, making these extreme cold events noteworthy interruptions to that general trend.

Specific locations along Lake Michigan have recently documented similar formations following intense cold. In mid-January 2025, pancake ice was observed near Chicago, Illinois, during a period of dangerously cold weather. Furthermore, other West Michigan locations, including St. Joseph, South Haven, and Grand Haven, reported seeing these icy platters during a brutal cold snap in mid-January 2025. The observation near the North Pier Lighthouse on December 15, 2025, highlights the localized intensity of cold air outbreaks that can still produce these dramatic ice dynamics despite overall warming trends.

From a scientific perspective, the formation of pancake ice is significant as it influences ocean-atmosphere interactions by affecting wind friction and heat exchange across the water surface. Meteorologists and climate scientists monitor these events as indicators of active wave dynamics and freezing temperatures, which are crucial for understanding sea ice development and local weather patterns. The appearance of this ice structure, even temporarily, underscores the powerful, localized impact of extreme winter weather events on the physical state of the Great Lakes.