We live in zone 3 and we have to dig them up and store them for the winter.

Even in zone 5, I have to dig and store my tubers for the winter. I believe we are more southerly than you, but you are closer to the ocean than we are.

Personally, I would dig them up, and store them as advised on the dahlia forum of the garden web. Why take a chance on something you love so much?

as a matter of fact just yesterday I spoke to a world famous breeder and grower of dahlias since I just "discovered " them, and she told me, you must dig them up in the winter. Either the wet, or the freeze, will kill them otherwise... sigh... don't know if I will " do " dahlias after all... dont wanna dig in the fall... maybe chrysanthemums will suffice?

What a shame, blackgavotte. I know dahlias and cannas are some work, but the rewards outdo the efforts for me....especially the dahlias. This year I had a dahlia hedge along both sides of my outdoor fireplace. Stunning!
I've dug mine up, cleaned and dusted them, and packed them away until next April, when I'll start them indoors, and have at least 3 months of steady bloom. Next week, I'll pull my cannas and do the same for them. They can tolerate some frost.

I've found many different ways of storing dahlia tubers what has worked the best for people in Zone 3

I had always thought dahlias were annual bulbs and I had sworn never to plant anything that had to be dug up and replanted every year. Last year, i broke down and bought 2 bulbs. I planted them in our garden and nothing came up! Since we have heavy clay, I thought maybe they had rotted or been eaten by something. I never did bother to dig them up to find out what happened. Surprisingly, this year both came up. I was speaking to my SIL and she told me others had this happen to. They sure did multiply though. marg