I cover mine with a huge plastic bag.... leave the bottom loose so condensate doesn't form.... You can also throw a towel or something similar, over the control unit, then the plastic... It would still be better to put under an overhang or in a wood shed.... Also, an oven light bulb, in a trouble light, put inside the smoke before all the other stuff is done, will keep the moisture out and keep mildew from forming....
Dave
For the big bag, I went to my local tire dealer and got one of those bags they put your old tires in, for you to haul home...