According to the FL Department of Highway Safety and Motor Vehicles (HSMV), Canadian citizens are non-immigrants and are allowed to stay in the US without obtaining INS documentation.
If you want to register and insure your vehicle in Florida you will need a FL driver's license. The HSMV says that Canadians without INS documents must provide proof of Canadian citizenship to be issued a Florida driver license by presenting 2 of the following documents: Canadian passport, Canadian driver license, Original or certified Canadian birth certificate, Canadian Naturalization certificate.
Once you have your license it should be easier to obtain FL auto insurance and register your vehicle. Florida requires any part-time or seasonal resident living in FL for 90 days or more during the year to obtain a Florida personal injury (PIP) and property damage liability (PDL) auto insurance on their vehicle.
The HSMV notes that all out of state residents must have proof of Florida insurance before obtaining a FL license plate or registration renewal. Florida insurance is required to meet the requirements of Florida Statutes. Only insurance issued or countersigned by a Florida agent is electronically reported to the Department of Highway Safety and Motor Vehicles for verification purposes.
Once you get FL auto insurance you then can take your proof FL insurance, your original out of state title and the VIN (vehicle identification number) verification form (completed on an HSMV form that is available on their website) to a local FL county tax collector's office. This state agency should then be able to help you obtain Florida registration and license plates for the vehicle you plan to keep in Florida.
For the months that you are not in Florida you must continue to maintain insurance on your vehicle or surrender your Florida tag and registration at the nearest driver license or tag office. If you choose to do this, when you next return to Florida you can register the vehicle after you have obtained proof of FL insurance once again. Since it sounds as if you plan to leave your vehicle in Florida for the full year, then you will want to continue insurance on it for that whole time.
Once you get a Florida license, which most all auto insurance carriers will require, you can get a quote for Florida car insurance here with us. If you need more specific information on what paperwork you will need to bring from Ontario to register your car and leave it in Florida contact the FL HSMV whose representatives should be able to give you more information on your specific situation.