Its a long ride, you can always buy a warmer bag once you hit the mountains, you may find a fleece is a cheap way to add warmth once you hit the mountains in the west. Have a good trip. We are having the same dilema this year, starting in Montreal, where I think it will be hot and humid, then going east and north till we end in NFL. where I suspect it will be damp and cold. I think we will go with the cheap fleece and if necessary get some bags from the REI or MEC and shipped general delivery.