Better to wait until fall to move it, if you can.
You should wait until late fall, as Four Seasons suggest, and get as much of the root ball as you can.
Can it be split or does it have to be moved a whole? Thank you so much for your help.
What type of hydrangea do you have, Ann?
We had 4 huge ones, dug the rootball out, used a sharp shovel to split the ball. Planted them and they did great. We did it in the winter.