Yup, they are definitely a problem. Really, if you want to realistically miss them, I think you're looking at the Fall. Depending on the area, its probably not as bad as Michigan, but you won't avoid them by taking a different route. Even at altitude you'll find some of them. And when you talk the North in the Summer, they will be everywhere. Lots and lots of water in Northern Canada.
I don't know if they would ruin a trip, but they will be a factor.
Hope you have a great trip.
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