Usually for colder zone like yours, advice is against pruning a young fruit tree heading into winter as it could weaken a tree and make it more susceptible to winter damage.

Your tree is not in this category. However, a tree responds dfifferenty at different pruning time of the year.

It also depends on how much pruning you plan to do. If it's light pruning, it probably does not hurt.

If it was a lot of pruning and it were my tree in zone 5, I'll wait till early spring.

Thank you, eastmeetwest. It would be mainly getting rid of this summer's vertical shoots. It is pruned into a large umbrella, and the main shaping has been done in earlier years.