the garage

Well it really depends on the construction of the garage, doesn't it? (Is this a top secret location?) If the garage has drywall walls and ceiling, an insulated roof, and a tight-fitting door, they should be fine. Otherwise, you might want to consider a well built (concrete block) personal storage unit for the year.

I'd bag them in polyethylene anyway, and include a bag of dessicant. Also set them on pallets to guard against flooding or damp floors.

Consider that they originally came to the dealer in a truck, bouncing down a highway at 75mph or better. Before that they were shoved into a metal container that came from France across the high seas in more than humid conditions.
Handeled by dock workers that only cared about filling the manifest. I would just seal the boxes set them on a pedastel incase of water getting on the floor. Maybe as a precaution cover the boxes with plastic to keep the cardboard from getting distorted for resale down the road.

Yea, better bring 'em over to my house. I'll keep them climate controlled for you. Seriously the humidity is worse than the heat. I would keep them in the house especially if near the coast. But really the manufacturer will advise you best.

only if the garage is climate controlled and well off the floor. any place with the 'radical' season change will have potential dampness and mildew. same goes for your music collection. the smell alone will last longer than the equipment. keep in in the house if at all possible in the coolest, most low traffic room.

Sam, Over time, the high heat and humidity will be hell on the adhesives used and the surrounds and cabinet joints. Lots of external insulation might keep the heat from getting to the innards but I'd still find room inside for your precious and valuable gear.

Are you to be without music for a year? Scarier still...