Inland climate in Canada and (for Scandinavia) the Gulf Stream could make the difference. Although I imagine the Hudson bay should give it more of seaside climate?
Mean daily temperature range (min to max): Cochrane -19c to +24c, Edmonton -15 to +23
Growing season: Cochrane 155 days, Edmonton 123 days
Frost free days: Cochrane 99 days, Edmonton 135 days
Precipitation: Cochrane 90cm, Edmonton 42cm
Around the first world war when the area was being settled, wikipedia quotes "7 months of snow, two months of rain, and the rest black flies and mosquitos. If I had to describe Edmonton, it would be 6 months of winter, one month of rain (June), 2 months of mosquitos, and 10 months of sun.
If I had to guess, the frost free days is a big factor. Even though Edmonton is further north, we benefit from the jet stream coming over the mountains and largely keeping the arctic air mass away from us. The jet stream tilts further south into the US by the time you get over to Ontario so Manitoba and Northern Ontario can get some bitterly cold winds.
Eg, Lillehammer, Norway is around the same latitude as Whitehorse, Canada but the average December high/low is a balmy -3°/°-8 compared to -10°/-18°. And Bergen is at the same latitude as those places but is even warmer, with a climate similar to Vancouver! That always amazes me.
As far as Hudson’s Bay being “seaside”, Churchill, Manitoba is on the southwest shore and is a great place to go and see polar bears.
If climate change does end up affecting the Gulf Stream, northern Europe is in for a tremendous cold shock.
[0] https://upload.wikimedia.org/wikipedia/commons/9/92/Annual_A...
But only 20000 years ago Sweden was covered in 3km of ice.