Question about temperature

The problem is not so much the cold temperature, but the change in temperatures.  As the temperature drops the ability of the air to retain moisture goes down. This results in the water coming out of the air as condensation or frost. This will result in rust on steel and possible other damage to other materials. It is a tough spot to be in.   Best storage for trains is cool, dry, and a constant temperature. The RH should never go above 40%. 

Pack the stuff in moisture-proof containers with insulation, and you should be okay.  The "insulation" can be the original boxes with inserts if you separate the contents from any styrofoam with acid-free tissue paper or plastic sleeves.  Some people use stackable plastic totes, but I used foot lockers (the wood ones with vinyl skins, not the plastic ones with holes under the handles) when faced with your predicament.

Suggest you find a closet or cabinet in the house for command control/sound equipped pieces.  I even tucked such pieces in a keepsake automobile parked in an attached garage with insulated walls to maintain a smaller temperature range when in need of temporary storage.

What, me worry? 

I  got back into the hobby about 10 years ago,before that time my trains were stored in the attic here in N.J. for 25,or 30 years with no fancy packageing,other than the boxes they came in,some items didn't even have a box,the track was the old o-27 steel track,i didn' have any of the modern loco's with all the fancy electronics,yet when i finally took them down from the attic & set them up,there wasn't any rust on the track,i really mean NOTHING at all & the few engines i had all started up with no problem at all,i don't know if todays modern loco's would work that easy,with all the electronics in them,i have my doubts that they would,my attic is not heated,or cooled.