We live in a dry climate, so it's only an issue if some klutz named Doug leaves stuff out in the rain or morning dew.
I usually keep an oily rag (from oil changes; used to be a T-shirt or sock) in the garden shed to wipe down any gear I care deeply about.
When it comes to shovels and hoes, I find the best way to prevent rust is to continually thrust them into the soil.