If you are looking to replace or repair hardwood floors, it is not a bad idea to get it done during the winter. Even though you might have to keep some windows open to ventilate the area, it will avoid the high chance of the floors warping due to how humid New York City gets in the summer.
Of course, it is not a good idea to repair your roof during a snowstorm, but if there is a hole or a possibility that the roof will leak if it snows or rains it needs to be replaced as soon as possible! The last thing you want is to have a weak roof during a blizzard and it caving in.
Sometimes, there are certain renovations that can be done during any time of the year, but might be problematic if they are done in the winter:
Although it is doable to renovate your kitchen in the winter, it is easier to do it in the summer because there are other ways to cook in the summer that do not involve a full kitchen, such as a grill or barbeque.
Doing anything outdoors such as fixing or adding on a deck will be a problem during the winter, but you should especially avoid doing outdoor renovations that are not necessary to get you through the cold weather.