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Canada's 2012 wasn't off the climactic charts like its neighbour to the south: While this was the hottest summer on record, it was only the fifth-hottest year overall.

But every region in the country had warmer weather than normal. And a swath of Central Canada from Windsor to Quebec City tied with 1998 for the warmest year ever – one punctuated by a soggy winter that wasn't and a sweltering summer.

Winters are seeing the most dramatic shifts. This year was Canada's third-warmest since 1948. Toronto recorded the warmest average winter temperature since 1840.

"We define Canada as winter – we're a land of ice and cold and snow. And yet the one season that's shown the most dramatic warming is winter," said Environment Canada's David Phillips.

"It was wacky warm here," said Daniel Scott, director of the University of Waterloo's Climate Change program.

Warmer winters create a positive feedback loop. High temperatures one year mean that heat is stored better and released more slowly the next, Prof. Scott said.

The trend's starting to have more serious implications than watery ice rinks and muddy tobogganing hills. Amid a warming globe, Canada and its Arctic are disproportionately affected: Melting permafrost means trouble for infrastructure up north; lower lake levels have both shipping and hydro implications.

Where climate scientists might have called for government prevention efforts, now they're calling for adaptation – long-term plans to build seawalls and irrigation systems as well as public-health systems prepared for extreme heat and a rise in vector-borne disease.

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