Are the stems still firm, or are they mushy? If firm then just remove the bad leaves and have patience...If mushy, cut back to firm tissue, assuming there is any left. You might try dusting the cuts with cinnamon...a good fungicide in a 'pinch'.

Dave
Milwaukee

It would all depend on just what kind of freeze hit the plants. Normally, geraniums cannot be hit with frost in the fall before they go into coolness.
An hour's bite of cold might not have inflicted too much damage so the first impulse is to cut back anything that is wilted, damaged or otherwise. They are now at the time when they should be renewed in any case so taking them back severely shouldn't upset the apple cart.

Unpotting them and inspecting their roots is the first thing to do...let's hope the roots are not showing frost.

Do you usually follow this approach to keeping them over winter---in the garage. I would think the garage door is opened for quite a spell sometimes, getting the shovels out and so on. Hopefully you do give them some protection from winter chill and wind. Most garages are not heated and thus have the ambient temperatures of the great outdoors.