An autumnal air in the alpine zone

Crossing the tree line and entering the alpine zone, I noticed that the Sorbus matsumurana have started to change color very slightly. I get the sense that the fall foliage season is not very far away. Even the so-called “Tasuki no Koyo” slope, which is popular as a place for viewing the autumn leaves, appears to me to have colored very faintly, although this cannot be discerned in the photo. Is it too early for the leaves to begin changing?
Photo: “Tasuki no Koyo” slope (Minamisawa), Mt. Midori Aug. 18