
Certified GKH Gardening Expert
It's best to wait till fall, after the foliage has died back, but since you live in an area without temperature extremes it should be OK.
You will need to take extra care to see that they are well watered before and after the move. When you dig them up, make sure you get most of the rootball to reduce the transplant shock.
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/transplanting-bulbs-in-gardens.htm
https://www.gardeningknowhow.com/ornamental/bulbs/dahlia/dahlia-care-grow-dahlia-plant.htm