Thank you for reaching out to ask2.extension.

I would dig them now before the ground freezes.

Remove the soil from the tubers by hand.  Let the tubers dry upside down for a few weeks. Store the tubers in trays or boxes filled with dry sand, compost, or soil, leaving the flower stalks exposed.  Place the trays in a cool, frost-free location, such as a shed or garage.  Make sure they stay dry and have good air circulation.

Good luck!