I recommend that the following shouldn’t be left in a garage, because what you decide to leave in a garage can be affected by the extreme climate conditions. Garages can get either hot, humid, cold, or damp, which can affect many types of products or materials. Even if the garage is heated, it’s usually not climate controlled enough to protect most non mechanical items. People usually leave their utility equipment, holiday ornaments, seasonal sporting goods, keepsake items, or overflow groceries from their most recent trip to the big box stores. The problem with storing anything in the garage, is that most items are forgotten after they are stored.Items are usually stored in a plastic bin or cardboard box labeled with a marker, stacked on a shelf, or worse, left on the floor. It's not until an extreme weather incident damages your items left in the garage.  That’s when you pay attention to them again. I suggest not to leaving the following items in a garage unless they are carefully packed and protected from any conditions. Here is a list of things I wouldn’t advise leaving in a garage:

Don’t leave anything too valuable in a garage without completely securing them. How many times have you left the garage door open? Unless you live in a wholesome and safe community, expensive bicycles, and fancy sporting equipment can tempt a less than trustworthy pedestrian.

Don’t leave products out where they can be affected by extreme weather. Whether they sit in hot or cold temperatures. Products can easily dry up or get moldy.

Don’t leave camping gear in a garage. Camping equipment, like tents and sleeping bags could get moldy and can also attract hungry mice. Mice are able to chew through the fabrics and ruin them.

Don’t leave fabric material open to the elements. You may want to take out grandma’s old prom dress to use as a Halloween costume, but you may find the fabric’s condition unwearable. Fabric can smell moldy, be torn by mice, or attract moths.

Don’t put paper in a garage. Storing a big filing cabinet filled with documents in a garage many seem like a good place, to keep them but Paper documents usually contain private and sensitive information. Having them open to the elements and easily accessible in a garage can tempt prying eyes or cause them to get damp and moldy if they get wet.

Don’t save books in a garage. Books may attract bugs and eat away the book binding and paper pages.

Don’t leave toys in a garage. Toys can cause dirt, dust to stick to them, and depending on how long they sit there, the plastics could get dry and brittle, making them crack.

Don’t leave perishable items in a garage. Items that may attract critters; No food or pet food.

Don't leave a car battery in a garage. If the garage is not insulated and climate controlled. Sitting too long in extreme weather can potentially freeze the battery.

Don't leave oily rags out in the open. because oily rags can easily combust when the heat rises. It’s best to store oily rags in small, airtight, non-combustible metal containers.
Let me know if you need any more information! I am happy to  speak with you more about how to best use a garage for storage.