D.N.
You should be able to go to a craft store and buy a bottle of temporary adhesive. At the store we go to, it comes in a bottle with a dabber/roll-on type. And yes, if the outside wall gets really cold, they can start to fall off a bit. If your local home improvement store sells the wall-stickons you might be able to get the temp adhesive there as well. I think some brands also come as a spray (similar to spray paint)