I have moved a mature rhubarb clump during the warm-weather season (May--after one harvest) with success; new growth was slowed down the rest of the season.

But during the hot weather coming up, I wouldn't advise it.

More commonly, the rhubarb would be allowed to stop growing for the year and the stalks and leaves then flatten and decay on the ground (around 1 November). Then it could be moved then or until march when growth restarts.

Don't forget to cut out bloom stalks when they appear; this does not happen every year.

Consistently-watered rhubarb can be harvested through the summer, rather than one May/June harvest for combining with strawberries.