Fall colors in Michigan peak in October. Here’s the map that most everyone uses to show the approximate times of peak color:
However, I’ve generally found these dates to be too early. In my notes, I have the AVERAGE date of peak color in Grand Rapids as Oct. 18. Colors will peak a little earlier to the north (U.P.) and in higher elevations and a little later when the prevailing wind off Lake Michigan delays the first frost along the lakeshore.
Generally, color comes early when it’s generally cloudy (trees respond to shortening daylight) and a few days later when the weather is more sunny and warm with ample rain (trees will lose leaves in a drought even in the summer).
Also – From Grand Rapids Magazine: County road agencies unveil best roads to see fall colors.