Not limited to northern states. Here in Louisiana our winters are very mild yet most road construction occurs during the summer. Why? Who knows. Construction could easily be conducted during the winter and there would be more out of state contractors willing to bid on jobs and more workers available. Nice to keep our local contractors busy but it would at least force them to lower their prices.
A bridge over the Mississippi River near us has had ongoing construction by our DOT personnel for a few months now. They tear up the surface one day then about a week later they resurface it. Then after a couple weeks paint lines on one side. Then a couple weeks later paint the signs on the other side. Then along comes the parish and digs up the new road surface to lay a new drainage line. Wash, rinse, and repeat. Deja Vu all over again.
Meanwhile there is major multi year construction on I-10 at Baton Rouge that will force traffic down to 1 lane on both east and westbound lanes. Just a heads up for anyone traveling through BR this summer.