The grading winter thing is not my idea, ive participated and seen them over the years here on the forum.
And i think it should be a subjective thing because its a personal experience to everyone and there's so many factors. Making it based on hard data and climo sites would just be boring. I mean, we arent doing it for anything much more than entertainment and to talk about it, it's something just for fun.
I believe it was always based on the entire snow season for the northeast, whenever the first and last snow was, not met winter.