Storing your skis properly in the Summer can help your skis last much longer. Even if you're replacing your skis every year (cough cough and buying them from The Ski Monster cough cough) having your back up pair or 'rock skis' in better shape is always a good thing. When thinking about where you should store your skis in the Summer, think about where you would keep your dog if you were to run out for a long day of errands. You wouldn't put your dog in the garage, it's hot in there. You wouldn't put your dog in the attic either, that's way too hot and a little weird. The Basement, sure if there is carpet or a mat for it to lay down and rest on. Don't forget the dog needs food and water too.
Food and water to a dog is what wax is to skis. Skis should be waxed prior to storing them for the Summer. Don't worry about scraping, the excess wax is a great protective barrier. The wax on the skis will help keep the moisture in the bases, the excess wax on the edges will keep them from getting rusty and gross.
Dogs don't like to be hot and neither do skis. Keeping your skis in the garage or attic can cause them to sweat, that little bit of moisture the skis have in their bases that's keeping them healthy wants to get out. If you have ever noticed the bases of your skis looking white and fuzzy it's because they are dry aka unhealthy.
The best place to store your skis during the off season is in a temperature controlled environment that is away from the sun; such as your bedroom, closet or even underneath your bed. It is best not to store them on concrete, the concrete releases a lot of moisture and can cause the edges closest to the concrete to rust. Treat your skis well and they will last much longer. Skis can only be tuned so many times, every time they are tuned material is taken away from the skis, keep your skis and healthy to get as much time out of them as possible.