I've had the best luck leaving them in the ground for a while after the first killing frost. I could be wrong, but it seems like the bulbs get a little bigger that way.
A week after the frost I may clip them back a little, then a week later dig them up and hose them off.

I've really enjoyed this fall, everthing still looks fairly decent. Our heads may hang low Friday?

I am still learning about dahlias but according to a big grower ... Swan Island, they said to leave them in the ground two weeks after frost takes the foliage. Supposedly the tubers ripen and they do better in storage. But this nursery is in the Pacific Northwest and I wonder if they know what we have to deal with here! I haven't lost any by digging them right after frost and my storage is less than ideal ... too warm. I think one of the keys to success is to check them during the winter and mist them if they are too dry. This year I was giving some very shrunken, less than hopeful tubers and they still did fine once they were 'plumped up'. They are magnificent in the late summer and fall. I have a heritage red I plant around my deck that everyone falls in love with.
Linda

I haven't gottem mine out yet so I hope that's okay. We only had our first frost 2 weeks ago so I assume they are still fine. I am not that keen on digging things up and planting them again. I do have one plant in the house in a pot with some gladiolas. What the heck should I do with those, put them in the basement or just keep them by a window!?! I put some in a pot since I am tired of the dig/replant cycle.

Marcia

I haven't grown dahlias for several years, just cannas now... but in my experience, it is best to dig the bulbs well after the killing frost. This gives them time to go fully dormant before being brought indoors.

If brought into the warmth immediately after the frost, the bulbs may try to resprout. This could seriously weaken the bulbs, and lessen their chances of surviving the winter.