I accidentally left 2 new packages of fondant in the car overnight. It was about -10C here. I have them thawing in the coldest place in the house right now to hopefully prevent condensation from forming.

Will they be okay to use? Any suggestions?

I always freeze my fondant wrapped in cling wrap and I have now problem. I normally defrost in the fridge but once I left it at room temp to defrost and I had no problem. It's very warm where I come from.