“Cold” is the new “warm”.
This past winter and early spring in the Great Lakes region would be closer to the normal climate in the colder 19th century. If we had graphs from 1871 to 1900 my guess is that this current ice cover would appear average rather than unusually high. Spring temperatures were colder in that era, relative to late 20th century normals that we use now, by 3-5 degrees.
As for Lake Nipigon being frozen, that would not be too unusual. It’s a relatively shallow lake and being further north has much colder mean temperatures through the winter season. Some lakes as far south as Georgian Bay to the Ottawa valley have remained frozen in May in past years. I can recall the ice going out of a lake just a hundred miles north of Toronto about this time of year in the 1970s when we had a run of colder winters.
Friday’s high of 45 at ORD was 25 degrees below normal and missed the record by one degree; that was set in 1891.