FWIW Our boat is in Manitoba
What we do:
- Use a shop vac to get any remaining water out of the "bilge" (such that it has one)
- Dump the water out the 5 gallon portable potable water tank
- Empty both porta-potti tanks, then put RV antifreeze in the porta-potti and pump it a few times so it gets into the pump.
-Put a few bags of "Fresh Cab" rodent repellent around the cabin
-remove and store all the cushions indoors
- use trailer support jacks at the rear of the trailer to help take load off the tires.
The last 2 winters we simply had a tarp over the mast above the cockpit, with a support in the middle of the cockpit. This was to help keep the snow out of the cockpit, without any ill effects.
That said, Southern Ontario is much more prone to moisture and the moderate temperatures that can lead to heavy snow, ice and a longer freeze/thaw cycle. The snow here is usually dry and once the winter hits, it usually doesn't melt until spring, so it has not been an issue.
Regardless, I am in last stages of sewing a full cover for future use.
If you have never been to Toronto in February, trust me it gets damn cold.
Torontonians have no idea what cold is, and we have no idea why they call out the army during snow storms
Seriously though.. the damp is an issue. I found the winter in Ottawa to be much worse than in Winnipeg, in regards to feeling cold, even though it has warmer winter temps. This is likely because you can't seem to keep the damp out from the higher humidity.
It's those warmer temps, and the longer freeze thaw cycle before and after winter, that will likely cause problems. Due to low temps/low humidity, the snow load on the deck here isn't usually an issue, though there have been occasional years when you needed to go clear off excess snow.