I live in the Deep South where things get moldy and slimy if you glance at them sideways. I made breathable storage bags for both the water hose and power cord (the latter gets plenty wet if the rig is hooked up in the rain).
Thumbnail of the bags middle left (this image was from a van accessory DIY contest that I did not win), and blog post here
with simple sewing instructions. Some people buy canvas bags off the shelf, for the same reason - breathability.