What Is Lake-Effect Snow And How Does It Form?

Here Is The Science Behind Lake-Effect Snow

Late-fall into winter is when the lake-effect snow machine kicks into gear again — and it's not just around the Great Lakes.

Let's dive into the science behind lake-effect snow, how it creates such extreme totals and where we can see it across the country.

The Classic Setup

Meteorologists know a lake-effect snow event is on the way based on the distinct setup.

The pattern features a sharp plunge of the jet stream anchored over the eastern U.S. by an area of low pressure over or near Canada's Hudson Bay.

This causes repeated rounds of cold air to spill over the Great Lakes and create bands of heavy lake-effect snow off lakes Erie, Ontario, Huron, Michigan and Superior.

The Science Behind Lake-Effect Snow

In the simplest form: warm lake waters plus cold air aloft equals snowfall.

But by warm, we don't mean the lake waters are prime for swimming. They are just mild enough to create the temperature contrast needed with the colder air above in order to form clouds, then snowflakes.

Ideally, that setup will feature temperatures around 5,000 feet above the ground that are at least 23 degrees Fahrenheit colder than the lake temperature.

The lake adds warmth and moisture, which evaporates into the colder air above, resulting in condensation that forms clouds and bands of lake-effect snow.

This temperature contrast is most likely to happen from late fall into early winter, before lake waters turn colder or even at least partially ice over, especially Lake Erie.

For example, in a span of 10 miles, a driver might go from wide-open visibility and no snow to near-whiteout conditions and then back to no snow after exiting the band.

But even though the bands are narrow, they can have impacts far inland at times.

The length of the bands of snow ranges from tens of miles to more than 200 miles long, depending on how strong the winds are to carry it inland.

Extreme Totals

Multi-inch snowfall totals in a single hour aren't unheard of in the most persistent lake-effect snow events. It's the reason why many of the most extreme U.S. snowfall rate records have occurred during lake-effect snow events.

December 2022 was a reminder that extended bouts of lake-effect snow can create serious impacts. A blizzard-inducing snow band from Lake Erie waffled over Buffalo, New York, for almost 72 hours around Christmas, dumping up to 51 inches of snow on the metro area, which buried roads, trapped motorists and shut down the city's airport.

Over a 10-day period from Feb. 3-12, 2007, Lake Ontario produced an incredible 141 inches of snow in the town of Redfield, New York, about 50 miles northeast of Syracuse.

It Can Happen In Other Places, Too ...

We see occasional bouts of lake-effect snow from Utah's Great Salt Lake and Lake Tahoe along the California/Nevada border during most winters.

Even smaller lakes can produce snow on rare occasions during extreme arctic cold outbreaks. One recent example was during a mid-January 2024 cold snap that allowed lakes in the Dallas-Fort Worth Metroplex to produce light accumulating snow.

Ocean-effect snow is also occasionally seen on the U.S. East Coast, especially along Cape Cod in Massachusetts.

Caitlin Kaiser graduated from the Georgia Institute of Technology with both an undergraduate and graduate degree in Earth and Atmospheric Sciences before starting her career as a digital meteorologist with weather.com.