Sept 1 is the first day of Autumn in NH, Dec 1 the first day of Winter. The first leaves have started to fall, though these are only from the weakened trees, and there is no foliage color yet. Oh, I imagine there are swamp maples up in the Lakes Region that are turning, but very little change of color here.
We are going into the 30's tonight, but nothing like John-Adrian's travails in Nome, where it has gone below freezing several nights already. I guess in Nome August 15 is the first day of fall and the equinox is the beginning of winter.