Don't you have a spare room in your house to put it in? I bring in my machines every night, i like to clean the inside of the waste tank and rinse out the pump (as you should to prelong the life of the pump) so needs to be done indoors anyways.
For the winter, you'll need to take in your solution hose, and anything with a valve! i.e. wands, hand tools and sprayers. And if you carry protector then this will be screwed if frozen.... Powdered detergants will be fine and so will liquids (apart from protector!)
Tony