Geraniums (actually pelargoniums, see the FAQs if you want the expalanation of the difference) need to be brought in before hard freeze. They can take light freeze if they are covered at night with an old blanket, or a couple of bedsheets.

They can be grown indoors as houseplants, and will reward you with beautiful blooms to enjoy all winter, as they would in their native Africa. I grow mine in a lightly heated sunroom all winter, because it's got nice light. They'd like a bit more warmth to put out more blooms, but they survive winter nicely in there. If you are blessed with bright southern windows in your house, they'll really do well.