Clean it, bag it, store it upright
The best way to store a box fan for winter is to clean the blades and grille, let it dry completely, then seal it in a large plastic bag or plastic bin, and store it upright in a dry place.
Don’t just shove it in a closet. Dust that sits over months can trap humidity and grow mold. A dirty fan also becomes unbalanced — that wobble and rattle next summer is from dust buildup.
Use a vacuum with a brush attachment to get the grille and blades. Wipe them down with a damp cloth if needed, then let it dry fully — even a little moisture in a sealed bag equals mildew. Stick the fan in a clean garbage bag, twist the end, tape it shut. Or
