The Fall Festival in Nozawa Onsen is on September 8th and 9th
One of the biggest festivals in the Village with some traditional ceremonies and fireworks
Probably a good lead in weekend on September 6 and 7th too with some Hiking and Mountain Biking and soaking in the Onsens
Lodge Nagano is doing a special from 2000 yen per person per night from now right thru til December 1st so get up any time to relax and enjoy the cool tranquility of the mountains and the beautiful changing colors of the leaves
http://www.lodgenagano.com/
The Fall Festival in Nozawa Onsen is on September 8th and 9th