You will be fine in September in all places you mentioned. As others mentioned, weather is always unpredictable. Any snow would most likely melt away completely during the day and immensely add to the scenery, your experience. Just count on your furnace for some below freezing nights. Daytime will likely be jacket weather. It is actually a great time to travel to the places you mentioned. It is my favorite time of year for that, after all the families return home and the kids back in school. I'd go out there in September in a jiff. Do you have room for one more? Ha, ha.