US/Canada Winter

Myself and my partner are in the process of trying to organise a 5-6 week trip to the US & Canada in Dec 2012-Jan 2013. This is obviously American winter.
We're looking to do New York first, then up into Boston and through French Canada (Quebec City & Montreal), across to Toronto and Niagara Falls. Then fly over to Vegas for New Years, a bit of snow skiing in the mountains before San Francisco, down the California coast to LA, then a stop-over in Hawaii on the way back.
We've got it all worked out (Contiki for the Vegas onwards part) except the part from Boston - Toronto. I can't find any operators (Contiki, Trafalgar etc) that run any tours up there during the winter.
Has anyone been to Canada in the Winter? How cold is it, and does anyone have any tips for the best/easiest way to see Ontario & Quebec?
We're looking to do New York first, then up into Boston and through French Canada (Quebec City & Montreal), across to Toronto and Niagara Falls. Then fly over to Vegas for New Years, a bit of snow skiing in the mountains before San Francisco, down the California coast to LA, then a stop-over in Hawaii on the way back.
We've got it all worked out (Contiki for the Vegas onwards part) except the part from Boston - Toronto. I can't find any operators (Contiki, Trafalgar etc) that run any tours up there during the winter.
Has anyone been to Canada in the Winter? How cold is it, and does anyone have any tips for the best/easiest way to see Ontario & Quebec?