I definitely experienced some weird days when I lived in the Toronto area. I recall wearing t-shirts outside some days in February and like a week later it was -20C again. The western part of Canada gets something called the Chinook Wind which also creates a weird local weather effect.
I've never seen the frozen ocean before, other than maybe looking out an airplane window. Ontario does have a railroad going up to the ocean, ending at a small town called Moosonee, but I don't know anyone that's ever been up that far. I'm not even sure you can drive up there except during winter and running out of gas would be fatal.
The Chinook wind is called the Föhn effect in Europe. That's what makes Alberta warmer than the more easterly continental provinces.
Although the Föhn effect caused by the Scandinavian mountains is somewhat attenuated when it reaches Finland, it may still cause notable warm spells in the western and the northwestern parts of the country in particular.
Moosonee is at the southern tip of James Bay, which is a southern extension of Hudson Bay.
There could be a winter road to Moosonee from the south. Google Maps shows a road between Moosonee and some more northerly localities along the shore.
I've watched Ice Road Truckers. It's a fascinating show. Those people have to deal with some pretty extreme conditions.
Trying to drive up there would be ill-advised indeed. You could bring enough fuel with you but your car could break down or the road might be impassable or too dangerous to drive on.