They developed quite differently. Boston, of course, was right on the shore and developed at a time that the distancea were significantly magnified as the horse was the only means of transportation. Common roads like Mass ave were continued outwards and places like Arlington sprung up. This lent itself to mass transit easily when technolgy caught up.

Greater Pittsburgh developed as mill towns. When Carnegie needed another mill, he looked for the next flat area near the rivers, took a steam ship to the European country struggling the most, and brought 5k or so people over. Built the mill, connected to the railroad, and built a town for them usually in their native language with English subtitles on signs. There was no interest in being connected to anything other than the mill, river, and railroad. They are suburbs now. They were fully independent towns (albeit company towns) then.

Not sure what this has to do with weather. But it does explain the ratio of suburbs to city.