I visited Prescott on Wednesday and the fall colors are in full swing, and there is still time to come see it for yourself before the leaves are all gone.
The trees surrounding Courthouse Plaza in Downtown Prescott & Whiskey Row are beautiful and it seems like they will be this way for at least another week.

I also hiked a portion of the Prescott Mile-High Trail System just south of Watson Lake. It was a mostly flat trail which you can follow to and from the south boat ramp at Watson Lake. The trails meandered through the trees, along a small creek and a few ponds. If you go, there is a $3 fee for parking.
