I grew up in Michigan too, my siblings all live in central Michigan. Their season is a at least couple of weeks shorter on both ends. Ha, ha, ha!!!!
I didn't put the peas inside cold frames, but I did have bird frames, as our lovely cardinals truly adored our peas. When frost threatened, the drop cloths would come out. They draped very nicely, with the help of some good old fashioned clip clothes pins, over those frames, especially if I happened to use the old flannel sheets.
Remember when planning your fall garden to account for the shortening day lengths of the season. You must add time that you would not need in the spring, when the days are lengthening.