As far as hikes go, South Sister is a non-technical summit and I felt very comfortable doing it solo. In early October, most of the snow is gone, and the weather has not yet turned to cold. In fact, I was almost afraid I didn't bring enough water, it was so hot.
Towards the summit in fall season, the route is covered in scree. At a few points, I felt that for every step I took up the mountain, I would slide two feet back down. Despite the heat and scree, it was a very enjoyable day and not nearly as tiring as my Mt Adams summit earlier in the summer.
View of the approach.
The views get more beautiful the higher you go.
A stunning panoramaic view.