When my neighbour bought his house, the equip had been left outside AND full of water for the entire winter, it still fired up and worked for 2 years after that, however, I would not recommend it.
a tarp is a good thing - probably as good as storing in a shed - the stuff is meant to be outside, so it will likely be ok, however, it's not much workfor me to throw it into the trailer and haul it to my garage which is always above 0c (32f)