The leaves are turning where I was/am (Davison, MI and Saint Clair, MI) as I type.. THis is my favorite time of the year and that has nothing to do with pumpkins.
Just went up to Mackinaw City 2 days ago. Leaves were just very slightly starting to turn. With some cooler weather coming up at night, I would probably think peak in about 3 weeks.
We have put of fall color trip plans together. Will be 12-16 days depending on the weather. Good weather will stay in some spots longer, bad weather less time.