I have one of the first Amerique's to come off the assembly line and it resides on my open front porch. I have a blanket that I put over it but it is nothing fancy. When the wind blows in the snow and drizzle I just take off the blanket and shake off the accumulations.
Last night is was 20 degrees here and I put on a 14# brisket at 11:00 pm at 235 degrees. The probe was set at 190 and shut about 9:15 am just after I woke up.
I have no problems with moisture in the display so I don't think it is your garage as my porch is even more of a hostile environment.
BTW, the brisket was my best ever. Used nothing but the Amerique, two wood chips, and liberal amounts of Cookshack Brisket Rub. I can not use my Amerique in competition or you all would be in trouble on the circuit.