ben:

This is the worst time. Wait until the tree is dormant, no leaves, and soil not too wet or dry. In Zone 5 you might try fall as soon as most leaves are off the tree. Otherwise in spring as soon as the soil is dry enough.

I agree with FN but if you fall transplant be sure to apply a thick layer of wood chips or other mulch at base of trees well beyond the rootsystem.

I transplanted 3 fruit trees yesterday, 2 sweet cherry & an apricot. They were planted bare root in late May, started doing well then the rains started. The spot where they were planted would normally be relatively dry but this year it's a mud bog...strange weather year. You could see them starting to wilt from drowning. Had a choice...let them drown or try transplanting.....they would never make it until fall...tried transplanting. As hman & fn say this is definately not the optimal time to transplant but sometimes you gotta do what you gotta do. Hope they live but if not I'll replant new ones next year.

If these were my plants, I will mulch them well for the winter without disturbing them in the fall and transplant them in the spring before breaking dormancy.

Here in Z6, I fall transplant bare root fruit trees by the score every year, most of them good sized, bearing age trees. I believe it to work better than spring planting but I do it because it's when I have time. In the spring there's just too much to do and the majority of fruit trees I plant then are the whips that I sell several years later as mature trees.

I started doing this many years ago when all the literature claimed spring planting was the only safe way to go this far north. That literature was just plain wrong, IMO, and I've used this timing preceding cold winters more typical of Z5.