What is lake effect snow? And why do Rochester and Buffalo get crazy amounts?

Lake effect snow. It's a part of what makes western New York winters feel like a wintry wonderland that requires daily shoveling.

Rochester, Buffalo and other communities along the southern and eastern sides of Lake Ontario and Lake Erie are known for getting hit by huge amounts of snow. 

But what, exactly, is lake effect snow? How does it happen? And why do we get so much? 

What is lake effect snow? 

When snow piles up in places such as Rochester and Buffalo in western New York or Marquette in the Upper Peninsula of Michigan, people start talking about the lake effect.

Lake effect snow, which can last for only a few minutes or a range spanning several days, develops from narrow bands of clouds that form when cold, dry arctic air passes over a large, relatively mild lake.

As the cold air passes over the unfrozen and "warm" waters of the Great Lakes, warmth and moisture are transferred into the lowest portion of the atmosphere, the National Weather Service says. The air rises, and clouds form and grow into narrow bands that produce 2 to 3 inches of snow an hour or more.

Wind direction is also a key component in determining which areas will receive lake-effect snow. Heavy snow may be falling in one spot, while the sun may be shining just a mile or two away in either direction. 

In Buffalo, the region receives most of its lake effect snow from Lake Erie, while Rochester's lake effect snow comes from Lake Ontario, said Jim Mitchell, a meteorologist with the National Weather Service in Buffalo.

Buffalo tends to see fewer, but more intense bands of lake effect snow, resulting in larger amounts of heavy snow that can deposit up to 4 inches an hour.

Rochester, on the other hand, sees smaller but more frequent amounts of lake effect snow, often lasting days at a time, Mitchell said.

"The lakes certainly keep up busy," he said.

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These snows typically occur only in the fall or early winter, before the lakes freeze over. (But if the lakes don't freeze, lake effect snow can occur throughout the winter and into the spring.)

Lake-effect snow records

How snowy? In the lake effect parts of western New York state, for instance, Buffalo, Syracuse and Rochester annually top the nation's list of snowiest big cities, each averaging more than 8 feet a year because of their proximity to lakes Erie and Ontario. 

The three cities vie each winter for the "Golden Snowball," awarded to the region's snowiest city.

Nearly unimaginable snowfalls have occurred in New York thanks to lake effect snow: The tiny town of Montague, downwind from Lake Ontario, holds the "unofficial" world record 24-hour snowfall total of nearly 6½ feet, set on Jan. 11-12, 1997.

And a crazy total of 5 inches of snow was once reported in just 20 minutes in Turin, Lewis County. Why crazy? Typically, a snow total of 2 to 3 inches an hour is considered "heavy." 

Sometimes lake effect snow clouds develop enough up-and-down motion to create thundersnow — a snowstorm with thunder and lightning.

Though the nation's heaviest lake effect snow falls around the Great Lakes, it also falls on other places, especially near the Great Salt Lake in Utah.

People who live where lake effect snow is common take the prodigious snowfalls in stride: As a Syracuse resident was quoted as saying in the book "Lake Effect: Tales of Large Lakes, Arctic Winds and Recurrent Snows": "We have no natural disasters. We never have to worry about hurricanes. Very rarely a flood. I can live with the occasional snowstorm. Then you can get out there and ski."

Contributing: USA Today Network