Outside winter storage in the Northeast is fairly vicious.
In addition to all the good info already posted...
Keeping the tank full of stabilized fuel is important.
You should be prepared for mice and the damage they leave.
The battery should be stored in a clean dry area and trickeled once a month.
The cover will abrade whatever it contacts, paint included, so maybe tape some chunks of foam onto the high spots where the tarp will rub. Make sure the cover will breath or moisture will accumulate and puddle.
I, personally would fog the valvetrain, pull the glowplugs and oil the bores and tape up the exhaust.
If you can it would be good to block the axel's off the ground and once a week turn the wheels by hand to keep the rust off the seals.
Make sure the vents are not in the path of dripping water.
Smear a decent coat of grease on any exposed cylinder rods, including the steering rack.
Attach a penguin float because if this rain keeps up you may need to locate your submerged tractor to use as anchorage. There is an old man with a long beard muttering something about cubits and gathering wood in my driveway.
Maybe a bit of overkill but you did ask for opinions and like the saying goes, everybody has one /forums/images/graemlins/grin.gif
All the best,
Martin