Well it is not always that cold and dry. There are many days when the temperature gets close to, or over the freezing mark. These days are relatively humid, and with your iron changing temperature at a different rate, the humidity condenses on it, creating ideal conditions for rust. If you put a tarp over the machine, it will make it even worse as you just put your machine in a green house.
The temperature swings go on all winter and may be even worse in the spring. By the time you are wanting to pull your machine out of storage you may end up with a nasty surprise.
I have dealt with this for many years, having my tools in the leaky old shed. Even the new shop will have no heat in it this winter. I can't do much about the temperature, but I sure can do something about the moisture and oxygen getting to the metal.
This video shows how I do it. My old jointer has been living neglected and in less than ideal circumstances for about a year now. A little attention is needed, so I hope you enjoy this, and maybe even it will help out a bit.
Thanks for dropping by