I recently bought a couple bags of white sugar on sale with expiring coupons. I don't bake much during the summer and I don't have AC so I'm afraid the humidity is going to turn them hard unless I can store the bags properly. (This has happened to me in the past.) I was thinking of putting them in zipper bags and storing in the freezer. Any better ideas?
I would put the sugar in glass jars with screw tops and store at room temperature. The main thing is to store the sugar in an airtight container. Plastic doesn't work well for this in my experience. If a long time has gone by before you use it, you may need to stir it up in order for it to flow again.
This is a caution for powdered sugar. Powdered sugar will get a stale taste if stored too long. I had an unopened bag in my cupboard for over six months and when I went to use it, there was a stale taste. Probably from the cornstarch that is in powdered sugar. I had to throw it away.
If you put the sugar in zipper freezer bags, you don't need to store in the freezer. The freezer bag should be enough to keep the humidity out.
I don't have fancy containers so I just wrap sugar in the plastic supermarket bag it came in.