Mine are spending the winter on the steps to the unfinished attic. I just checked and the temperature is 55, humidity 73%.
In spring I save the pieces I've cut off, so I can attempt to root them and get tubers, but they never amount to much. Last week I checked the 8 pots of cuttings and only two looked viable. I repotted with fresh soil, watered lightly and put them in the sunny kitchen bay window just to see if they'd grow. Time will tell. Then I found one clump of dahlias, no tag, in the shed. That also went to the same window to test how soon it will sprout, given the warm temperature and light. It's amusing what things dahlia people will do in winter.