How the warming Great Lakes could herald a new era of supercharged snowstorms

Sarah Bauer woke up to a shaking house.

She thought maybe an earthquake had struck near her home in Torrance, a village in Ontario’s cottage country.

But when she looked outside, she saw a massive tree had collapsed onto her driveway under the weight of rapidly accumulating snowfall, taking down a power line with it.

“It was freaky,” she said.

The storm that hit parts of central Ontario in late November and early December was the biggest in recent memory, meteorologists said, reportedly dumping a reported 140 centimetres on Gravenhurst, a town just south of Torrance.

Another round of intense lake-effect snow hit areas off Lake Huron again this week, with further squalls expected into the weekend.

Areas off the Great Lakes are used to big snowfall events, earning the title of Ontario’s snowbelt.

Yet something new is happening. Climate scientists and meteorologists say climate change, driven by the burning of fossil fuels, is helping create conditions that can strengthen the storms.

Richard Rood, a climate scientist who studies the Great Lakes, says lake-effect snowstorms will likely intensify as the planet warms.

“They’re probably better interpreted as typical of the future rather than extreme compared to the past,” said Rood, professor emeritus of climate and space sciences at the University of Michigan in Ann Arbor.

Lake-effect snow relies on a combination of an outbreak of Artic cold air and the comparatively warmer water of the Great Lakes. As the air passes over the lake, it picks up moisture and dumps it on communities downwind, in snowfall events often characterized by intense and localized squalls.

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Those storms are typical in late autumn or early winter, when lake temperatures are still relatively warm. By the depths of winter, ice cover helps to cut off evaporation, said meteorologist Arnold Ashton.

“Typically, you don’t get it quite as often in January, February — certainly in February — because you have more ice on the lake,” said Ashton, a senior meteorologist with Environment Canada.

But the warmer the lakes get, the more heat and moisture there is for those blasts of Artic air to pick up, intensifying snowfall. And as warmer winters limit the amount of ice cover, those storms may stretch deeper into the season.

“The Gravenhurst apocalyptic metre-and-a-half of snow was a late November, early December event … but with a warming climate, those events could linger,” Ashton said.

Gravenhurst was under a local state of emergency for more than two weeks as crews cleared snowed-in roads and tried to restore power to tens of thousands of customers. Stranded drivers had to be rescued from a highway that stayed partially closed for nearly three days.

After cutting up the collapsed tree across their driveway, Bauer’s family in Torrance bought one of the last generators available at a nearby Canadian Tire, she said in a recent interview.

It took four days for their power to come back on, she said, while for others it took more than a week.

“I’m really not used to getting this type of snow as quick as it came,” Bauer said.

Trying to predict the effects of a changing climate on winter weather comes with uncertainty, meteorologists say.

Warmer lakes could mean worse snowstorms. But as winters warm overall, it’s also possible that precipitation may increasingly come as rain. Fluctuating temperatures could mean some big snowfall events are followed by unseasonable warmth, raising the risk of winter flooding.

“In a nutshell, it’s a complicated issue and it really is kind of a foggy crystal ball into the future,” said Ashton.

A 2019 report by Canadian and American scientists suggested the Great Lakes basin over the past century had seen precipitation increases that outpaced the rest of the U.S., with more of it coming down in unusually large rain and snow events.

The Great Lakes entered this winter under one of their warmest stretches in recent decades, boosted in part by the hangover of the naturally recurring El Niño climate cycle, which peaked last winter.

Near the outset of December 2024, four of the five lakes had warmer average surface temperatures over the first 11 months of the year than any other in the past three decades, according to the U.S. National Oceanic and Atmospheric Administration.

Last winter also saw the lakes record some of their lowest ice coverage.

Intensifying lake-effect storms should give lakeside communities pause, said Rood, the climate scientist.

“It should really be motivating you to think about, ‘How can I manage the future storms?”

That’s just what officials in Gravenhurst are looking to do. A spokesperson for the municipality said a debrief meeting was being planned for this month. A report is also being prepared for town council about the storm’s cause and the local response.

Bauer said she was heartened to see neighbours supporting each other during the worst of it.

She recalled how someone in her area used a snowmobile to help rescue an elderly neighbour from her snowed-in home and then offered her a place to stay.

“You could see the community come together.”