5 months -- you will loose your Ontario health plan btw, so make sure you have proper insurance. You need your passport, of course. But proof of ties to Canada? Never heard of that one. Your passport proves you are Canadian. Keep the original in a very safe place while in the US. If you are in one city for most of the time, maybe a bank deposit box. Keep a photocopy of the main picture page with COPY written on it -- keep that one with you everywhere you go, perhaps with the name of the bank where the original is.
If you are concerned, you should contact the Canadian Embassy in Ottawa and they can fill you in with more details.