Sadly, few older women who are sewing knowledgeable are at places like wally's or even some real fabric shops. The younger ones generally don't know enough to help you find what you want.
Look on the end of the bolt for a lable as to origin and content. Some sheeting, some ticking, denim, canvas, and linen may work fine if woven tightly. Most of these goods have sizing (like starch) applied to the cloth as it is finished and pressed in manufacture. When you wash it a time or two, it will "fluff" up a little drying. Here in NC winters are less humid because of heating and summers more humid because of AC. Cotton expands (thickens) in summer, contracts(gets tighter) in winter. Measurements change, but I don't change what the load is using. Lon