To amplify Quora User's excellent answer: Boston has a higher average wind speed than Toronto (by about 3mph/5kph); not a huge difference but roughly enough to make the two cities “feel” similar to exposed skin, despite Boston's slightly higher actual air temp. read more
Having lived in Boston and visited Toronto often during winter I’d have to say Toronto is the colder of the two during the winter. read more
However, other aspects of Halifax's winter can make it seem colder. From December through March there's nearly 150% more precipitation than in Toronto (some in heavy snowfalls, but also frigid, heavy rain) which often falls during cyclonic ocean storms (noreasters). Halifax is also slower to warm up in the spring. read more
Montreal is farther north, so it gets much colder in the winter than Toronto. Toronto’s winter weather is seasonable and quite similar to that of the New England area in the United States. It doesn’t become a land of frozen tundra when the cold months come like Montreal. read more