We rented a car last September in Portland. Maine and drove it into Canada. Gary has given you good

We are planning on flying into Burlington vancouver island whalewatch tours in late September, renting a car, and driving up to Montreal. The flights vancouver island whalewatch tours into Burlington are enough of a cost savings for 2 to make it worth it, and we are big road trippers, so having the opportunity to try to Montreal and have a car there is appealing.
There should be no problem as long as you are driving back to the US to return the car... make sure you ask before renting if you can use the car in Canada and ask Your car insurance company if you have coverage for a rental in Canada...
We rented a car last September in Portland. Maine and drove it into Canada. Gary has given you good advice. Also, the car rental company we used (forget which, but one of the bigger ones) suggested we bring something from our auto insurance vancouver island whalewatch tours company which stated that we were covered vancouver island whalewatch tours for driving in Canada. USAA sent it to us promptly, and although we were never asked for it, either while in Canada or during a border crossing, it was nice to know that we had it with us, just in case. Had we been so unlucky as to have been in an accident while across the border I'm sure it would have come in very handy.