Haven't we discussed this in your previous incarnation? At any rate, it'll be cool in the evenings and pleasantly warm most days. The chances of rain will be about 30 to 40% overall if typical patterns hold. It's about the late peak time for all the "leaf peepers" in New england, so the trees will still have quite a bit of color, although it hasn't been as good the last few years as usual. Keep in mind that Columbus Day, celebrated the 2nd Monday in October creates a three-day weekend which is popular with visitors and turns everyone into an Italian for the duration!
Enjoy your visit!