Ask Mr. Smarty Plants

The quick answer is yes, it is too late.  It used to be said that in your part of the world you could only plant (or transplant) trees in months that have the letter "r" in their names.  That means that May through August are a no-go (too sunny, warm and dry).

But really ... it depends. 

It depends on: how big the tree you would like to move is (the smaller the tree, the greater chance of success), on what type of soil you have (rich, moist soil is better than dry, sandy soil), how hot the weather is (if it is cool and rainy or even overcast the tree will not transpire as much as if it is hot and sunny), how much native soil you manage to dig out with the tree roots (some trees, like apples, seem drop all their soil no matter how careful you are, so then transplanting them is essentially like planting a bare-root tree) and how much of the root system you dig out (if the transplanted tree does not have enough roots to deliver the necessary water and nutrients to the top, you should prune the tree accordingly, to improve the chances of survival).

Finally, it depends on how much risk you are willing to take.  If you can't stand the thought of losing the trees, then wait until early fall (when the soil is still warm enough for the tree to regenerate some of the root system and then go dormant for the winter).  If you can ... then go for it.

There are some videos on eHow regarding transplanting evergreens that you will find helpful.