We just put our trailer away in its rental spot in a farmer's field for the winter. I'm in Canada so we get some hardcore winters. Here's what we did:
- Made sure the tongue was higher up than the rear so that any rain and melted snow can run off
- Put a tarp that's a foot wider on each side over the roof
- put a 4x4 on the roof, under the tarp, 2/3 of the way up the trailer (closer to the tongue and beside the top vent) to create more of a peak. The wood also sticks out a bit on both sides so there's ventilation
- At the back the tarp goes all the way to the floor and we peaked it out behind the trailer (like the train of a wedding dress) so that there was more ventilation and we secured it to the ground with four cinder blocks
- Tied down the front of the tarp in the middle and the sides so that it wouldn't blow away.
Hopefully what I said makes sense. I neglected to take a photo so I tried my best to explain it well. Basically any water will run off, the roof between the tarp and the trailer can breathe, and it won't fly off.