Nikko is the 3rd largest "city" in Japan according to land size, therefore the ~40km x ~40km land area, 1,449.87 km2 to be exact, and 400m - 2578m above sea level makes picking the perfect time to visit Nikko completely dependent on where you want to go to see autumn leaves and fall foliage. Koyo in Japanese.

From the bottom of Ryuzu waterfall on the bridge on the main road is a wonderful view south toward Lake Chuzenji. At this point near the bottom of Ryuzu waterfall is a great time this year for the 1st two weeks of October....and according to reports, still nice into mid October.

This viewpoint is NOT on the trail from Senjogahara to Lake Chuzenji, you must go from the hiking trail through the parking area, to the bridge on the main road.