When does your flight depart?

I imagine you're planning to cross at one of the Buffalo/Niagara crossings. If you do have access to a maps program that shows traffic it is a good idea to check while approaching Buffalo to check which crossing has the best crossing conditions. When I lived there we'd often take the Rainbow Bridge crossing in Niagara but for high traffic times and holidays often the Peace Bridge would be better.

Depending on your flight departure time it may be advantageous to spend a night in the Buffalo area or Toronto ahead of your flight. I've had border crossings take all of 30 seconds and have had them take 2 hours (including waiting and questioning) but I have a US passport.