Hi Jools. I go to Michigan (which is further west I know) on private trips around that time of year.
Yes layers are defintely the way to go. The year before last we did a grand road trip to the U.P and then down the west coast of Lake Michigan and believe it or not the weather was touching 80 degrees all week. I hadn't taken enough t shirts so had to buy a couple.
Last year we did a shorter trip over from Detroit to Lake Ontario and Niagara. Warmer clothes were defintely right for that one! Then back to Michigan and the t shirts came out again. :thumbup:
Have a great trip!!