Hi,
I believe you'll find the weather will reflect what you have found on the internet - You'll be travelling on the cusp of the summer/autumn season change so you may find the temperatures in Canada to be between 11-18 degrees during the day but much cooler at night. In the states you'll be looking at daytime temperatures from around 15-25 degrees! And, as its that time of year there is a a chance of some rain too.
I know a few of our members have been on this trip, and I'm sure they'll share their hints and tips for packing.
Kindest regards,
Julia