Toronto does get to -20c in the winter it just isn't that common unless you include the windchill factor then it isn't that unusual to be in the -15 to -25 rang

Toronto does get to -20c in the winter it just isn't that common unless you include the windchill factor then it isn't that unusual to be in the -15 to -25 range (and very occasionally into the -30 to -35 range).