Hot weather is a very poor time to move any perennial, let alone Russian sage. It is very difficult to move Russian sage, as you cannot easily dig up the plant with the soil intact around the roots because the roots are woody and the soil falls off. It's much easier to move very small parts of the plant in the early spring.
If the plant is too large and has spread too much, dig up part of it and discard it, then wait until next spring and move new little plants that you may find or other small parts of the plant, which you can easily separate.
